WO2016079468A1

WO2016079468A1 - Filter, and apparatus and method for filter manufacture

Info

Publication number: WO2016079468A1
Application number: PCT/GB2015/053269
Authority: WO
Inventors: Kie Seon PARK
Original assignee: British American Tobacco Investments Ltd IFI; British American Tobacco Co Ltd
Current assignee: British American Tobacco Investments Ltd IFI
Priority date: 2014-11-21
Filing date: 2015-10-30
Publication date: 2016-05-26
Anticipated expiration: 2017-05-21
Also published as: GB201420730D0

Abstract

A filter for a smoking article comprising an extruded rod of filter material. The outer surface of the filter rod comprises a plurality of continuous open grooves extending in an axial direction of the rod. Also disclosed is an apparatus for manufacturing such filters. The apparatus comprises a duct having an inlet and an outlet. The duct tapers between the inlet and the outlet such that loose filter material and plasticiser fed into the inlet is compressed as it is conveyed through the duct into a rod which is expelled from the outlet. The duct is provided with a plurality of inwardly projecting elements to form grooves into the outer surface of the rod of filter material. The apparatus further comprising a heating region to cure plasticiser entrained with the filter material and thereby harden the grooved filter rod. Also disclosed is a method of manufacture of such filters.

Description

Filter, and Apparatus and Method for Filter Manufacture

Technical Field

In this specification there is described an apparatus and method for filter manufacture and, in particular, an apparatus and method for manufacture of grooved filters for use with smoking articles.

Background

Apparatuses and methods for manufacture of smoking article filters are known that comprise a continuous garniture belt that conveys filter tow material fed onto a continuous band of plug wrap though a tapering garniture duct or "tongue". Within the garniture tongue the garniture belt wraps the plug wrap around the filter tow material and compresses the material into a continuous cylindrical wrapped rod which can subsequently be cut to desired lengths.

It is also known to provide grooved filters in which elongate grooves are formed on the outer surface of the filter rod extending in the axial direction of the filter. Such grooves may be formed by applying a corrugated plug wrap around the filter so the plug wrap is impressed into the core of filter material, or by passing the wrapped filter rod though a subsequent groove-forming apparatus after it is expelled from the garniture tongue. Such wrapped grooved filter rods can suffer the drawback that the overlapping seam where the edges of the plug wrap and joined together, is stiffer than the rest of the plug wrap and can cause the resulting filter to be distorted into an oval shape rather than the desired circular shape.

Summary

In this specification there are described embodiments of a filter for a smoking article comprising an extruded rod of filter material wherein the outer surface of the filter rod comprises a plurality of continuous open grooves extending in an axial direction of the rod.

The filter may comprise a discrete filter element cut from a continuous extruded rod. The filter may comprise a single-length filter element for combining with a tobacco rod to make a single smoking article. The filter material may comprise cellulose acetate tow which is hardened with a plasticiser to provide a stiff filter.

The filter may not comprise any outer wrap around the rod of filter material.

The grooves maybe of uniform size and regularly spaced around the circumference of the filter rod.

The present invention also provides a smoking article comprising a tobacco rod and a filter as described above joined to one end of the tobacco rod.

The present invention also provides an apparatus for manufacturing extruded filters for smoking articles having continuous open grooves extending in an axial direction of the filter on an outer surface of the filter, the apparatus comprising a duct having an inlet and an outlet, the duct tapering between the inlet and the outlet such that loose filter material and plasticiser fed into the inlet is compressed as it is conveyed through the duct into a rod which is expelled from the outlet, wherein the duct is provided with a plurality of inwardly projecting elements to form grooves into the outer surface of the rod of filter material, the apparatus further comprising a heating region to cure plasticiser entrained with the filter material and thereby harden the grooved filter rod.

The apparatus may further comprise a source of compressed air associated with the duct configured to propel filter material fed into the inlet though the duct to and out of the outlet.

The heating region may comprise a steam supply to heat and harden the filter material and plasticiser.

The inwardly projecting elements may be of a uniform size and may be regularly spaced around the duct.

The duct may comprise a die on which the inwardly projecting elements are formed.

The die may be is detachable from the duct. The apparatus may further comprise a post-curing treatment station downstream of the heating region with respect to the conveyance direction of the extruded filter rod, the post-curing treatment station configured to provide the extruded filter rod with a smoother outer surface than the surface texture present when expelled from the heating station.

The post-curing treatment station may comprise an electrical heater configured to heat the outer surface of the filter rod sufficiently. The electrical heater may be configured to heat the outer surface of the filter rod to between 100 - 200 degrees Celsius.

The post-curing treatment station may be configured to melt the plasticiser on the outer surface of the filter rod so that the melted outer surface can subsequently set as a smooth finish. The post-curing treatment station may comprise a spray-coating station including a spray nozzle and a source of liquid treatment connected to the spray nozzle to spray the liquid treatment onto the outer surface of the filter rod to form a smooth outer coating.

The liquid treatment sprayed from the spray nozzle may comprise a plasticiser, and may comprise triacetate.

The apparatus may further comprise a cutting station configured to cut the continuous extruded filter rod into discrete filter rods having continuous open grooves on their outer surface.

The present invention also provides a method of manufacturing extruded filters for smoking articles having continuous open grooves extending in an axial direction of the filter on an outer surface of the filter, the method comprising feeding loose filter tow material entrained with a plasticiser into an inlet of a duct, the duct tapering between the inlet and an outlet, conveying the filter tow material through the duct such that it is compressed into a rod which is expelled from the outlet, forming grooves in the outer surface of the rod of filter material by means of a plurality of inwardly projecting elements formed in the duct, and heating the extruded filter rod at a heating region to cure plasticiser entrained with the filter material and thereby harden the grooved filter rod. The filter tow material may be fed into the inlet though the duct and out of the outlet using a source of compressed air fed into the duct.

The method may comprise heating and hardening the filter material and plasticiser in the heating region of the apparatus using steam.

The method may comprise forming the grooves a uniform size and regularly spaced around the filter rod. The method may further comprise performing a post-curing treatment on the extruded filter rod to provide the extruded filter rod with a smoother outer surface than the surface texture present when expelled from the heating region.

The post-curing treatment may comprise heating the outer surface of the filter rod with an electrical heater and smoothing the outer surface.

The post-curing treatment may comprise heating the outer surface sufficiently to melt the plasticiser on the outer surface of the filter rod and subsequently setting the melted outer surface as a smooth finish.

The method may comprise heating the outer surface of the filter rod to between 100 - 200 degrees Celsius.

The post-curing treatment may comprise spray-coating a liquid treatment onto the outer surface of the filter rod to form a smooth outer coating.

The method may comprise spraying a plasticiser, which may comprise triacetate, onto the outer surface of the filter rod. The method may further comprise cutting the continuous extruded filter rod into discrete filter rods having continuous open grooves on their outer surface.

Brief Description of the Drawings

Embodiments will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure l schematically shows a first embodiment of an apparatus of the invention; Figure 2 shows a cross-section through the apparatus of Figure l along the line X-X; Figure 3 shows a perspective view of a first embodiment of a filter rod of the invention manufactured using the apparatus of Figures 1 and 2;

Figure 4 schematically shows a second embodiment of an apparatus of the invention; Figure 5 shows a cross-sectional view along the line Y-Y as shown in Figure 4, of a second embodiment of a filter rod of the invention manufactured using the apparatus of Figure 4;

Figure 6 schematically shows a third embodiment of an apparatus of the invention; Figure 7 shows a cross-sectional view along the line Z-Z as shown in Figure 6, of a third embodiment of a filter rod of the invention manufactured using the apparatus of Figure 6;

Figure 8 shows a first embodiment of a smoking article including a filter rod of the invention;

Figure 9 schematically shows a fourth embodiment of an apparatus of the invention; and

Figure 10 shows a cross-sectional view along the line A-A as shown in Figure 9, of a first embodiment of a filter rod of the invention manufactured using the apparatus of Figure 9·

Detailed Description

Referring now to Figure 1, an apparatus 10 of a first embodiment is shown for the manufacture of filter rods of the invention, and comprises a duct 11 having an inlet 12 and an outlet 13, the duct narrowing from the inlet 12 to the outlet 13. A source of compressed air is provided to the duct 11 via a compressed air port 14 which, in use, propels filter tow material 25 into and through the duct 11.

The outlet 13 of the duct 11 comprises a die 15 having a central hole 16 and a plurality of projecting elements 17 which project inwardly from the inner wall of the die 15. This is shown more clearly in Figure 2.

A heating region in the form of a heating station 18 is provided at the outlet 13 of the duct 11 and comprises a passage 19 within an enclosed chamber 20. The chamber 20 includes an inlet pipe 21 and an outlet pipe 22. A source of dry steam (not shown) is connected to the inlet pipe 21 to supply hot dry steam to the chamber to heat the chamber and thereby the passage 19 and any material that may be conveyed through the passage 19.

A cutting station 23 is provided downstream of the heating station 18 and includes a cutting blade 24.

In use, filter tow material 25, such as cellulose acetate tow, is fed into the inlet 12 of the duct 11. The filter material is mixed with a plasticiser, such as triacetate, prior to being fed into the inlet 12 of the duct 11. The plasticiser is mixed with the filter tow 25 in a ratio of about 17% by weight, although other ratios of plasticiser may be used within the scope of the invention, such as between 4% and 50% by weight.

The filter tow material 25 with entrained plasticiser is conveyed through the duct 11 and out of the outlet 13 by jets of compressed air provided through the compressed air port 14. As the filter tow material 25 is conveyed through the duct 11, it is compressed as the duct narrows towards the outlet 13, to form a continuous cylindrical filter rod 26. As the continuous filter rod 26 passes out of the outlet 13 of the duct 11, it is extruded through the central hole 16 of the die 15, and the projecting elements 17 form continuous grooves in the outer surface of the continuous filter rod 26 extending in an axial direction of the continuous filter rod 26.

After passing out of the outlet 13 of the duct 11, the continuous grooved filter rod 26 passes to the heating station 18 and though the passage 19 within the enclosed chamber 20. Dry steam at around 170 degrees Celsius is supplied into the inlet pipe 21 and thereby into the chamber 20 where it comes into contact with the continuous grooved filter rod 26 within the chamber 20. The steam heats the filter tow material 25 and cures or substantially cures the entrained plasticiser so that the continuous grooved filter rod 26 hardens to form a stiff continuous grooved filter rod 27. The cooled steam is removed from the chamber 20 out of the outlet pipe 22, to be replaced by hot steam via the inlet pipe 21.

After the stiff continuous grooved filter rod 27 exits the heating station 18, it passes to the cutting station 23 where the cutting blade 24 cuts the stiff continuous grooved filter rod 27 into individual lengths of discrete grooved filter rods 30. These may be single filter length rods of size suitable for use in combination with a single tobacco rod to make a single smoking article. Alternatively, the discrete grooved filter rods 30 may be "2-up", "4-up" rods, or other lengths which are a multiple of a single length filter that would be finally combined with a tobacco rod to form a smoking article. Such multiple length filter rods can be supplied to subsequent smoking article manufacturing machinery to be cut to length in later processing steps.

A grooved filter rod 30 of the invention manufactured using the above-described apparatus and method is shown in Figure 3. The grooved filter rod 30 is substantially cylindrical with a central axis A-A and is continuous in cross-section along its length, and has continuous open grooves 31 extending in an axial direction of the filter rod 30, on the outer surface of the filter rod 30. The plurality of grooves are continuous along their entire length. That is, the grooves continuously uniform, and are not interrupted by raised portions, by being closed, or having any other form of blockage along their length. The grooved filter rods 30 of the invention manufactured using the above-described apparatus and method are sufficiently stiff and strong not to require any outer plug wrap layer to be applied to maintain their shape and structural integrity. As such, the filter rods 30 can be provided directly to a subsequent smoking article manufacturing process and the absence of requiring an outer plug wrap means the manufacturing process is simpler, quicker, more efficient and more cost effective than known filter rod manufacturing processes where a subsequent filter rod wrapping step is performed, which requires additional machinery and materials. The grooved filter rods 30 are also able to be manufactured to be accurately symmetrical about their central axis A-A, that is, accurately circular in cross-section. This is because the oval distortion caused by overlapping plug wrap seams of known wrapped grooved filters is avoided.

An apparatus 40 of a second embodiment for the manufacture of filter rods of the invention is shown in Figure 4 and is similar to the apparatus 10 of the first embodiment, and like features retain the same reference numerals and a detailed description of such like features will not be repeated. A difference with the apparatus 40 of the second embodiment over the apparatus 10 of the first embodiment is that the apparatus 40 of the second embodiment comprises a post-curing treatment station 41 disposed downstream of the heating station 18, with respect to the conveyance direction of the continuous grooved filter rod through the apparatus 40. The post- curing treatment station 41 is disposed upstream of the cutting station 23. The post-curing treatment station 41 is provided to smooth the outer surface of the continuous grooved filter rod 27 after it has passed out of the heating station 18 and has been hardened. The filter tow material 25 used to produce the filter rods 30 of the invention comprises many discrete filaments tangled together. Upon formation of the hardened continuous extruded grooved filter rod 27, some ends of the filaments may remain upstanding from the outer surface of the filter rod 27 and appear as fine upstanding "hairs". The post-curing treatment station 41 is therefore intended to provide a further treatment to the continuous grooved filter rod 27 to eliminate these hairs and to give the final discrete filter rods 30 a smoother outer finish.

The post-curing treatment station 41 comprises central passage 42 and electrical heater elements 43. In use, as the continuous grooved filter rod 27 passes from out of the heating station 18 and into the post-curing treatment station 41, the electrical heating elements 43 heat the filter rod 27 such that the tow material and plasticiser of the outermost surface of the filter rod 27 melts. This also causes any fine hairs upstanding on the outermost surface of the filter rod 26 to also melt. As the filter rod 27 exits the post-curing treatment station 41, the melted outer surface cools and hardens, forming a thin and smooth coating around the filter rod. The apparatus 40 is configured with the conveyance speed of the filter rod 27 and the power of the heating elements 43 such that only a thin outer surface of the filter rod 27 is melted in the post-curing treatments station and heat does not permeate far though the thickness of the filter rod 27, leaving the majority of the body of the filter rod 27 unaffected by the post-curing treatment. The heating process preferably heats the filter rod 27 to between 100 - 200 degrees Celsius. This range is optimum for being sufficiently hot to achieve melting of the plasticiser and tow, but not excessively hot as to overheat the filter rod 27 which could cause the material within the body of the filter rod to melt rather than just a thin outer layer, which would result in the filter being unusable as the internal melting of the filter rod 27 would render it impermeable.

Following the post-curing treatment station 41, the filter rod 27 is cut into discrete grooved filter rods 50 at a cutting station 23 as per the first embodiment of the apparatus 10 of the invention described previously. Figure 5 shows a cross-section of a second embodiment of the filter rod 50 of the invention made by the second embodiment of the apparatus 40 described above. The filter rod 50 includes a plurality of continuous open grooves 51 on its outer surface extending in an axial direction of the filter rod 50, and a thin smooth outer coating 52 formed by the melted and hardened tow and plasticiser as described above. An apparatus 60 of a third embodiment for the manufacture of filter rods of the invention is shown in Figure 6 and is similar to the apparatuses 10, 40 of the first and second embodiments, where like features retain the same reference numerals and description thereof will not be repeated. A difference with the apparatus 60 of the third embodiment over the apparatus 40 of the second embodiment is that the apparatus 60 of the third embodiment comprises a different configuration of post-curing treatment station 61 disposed downstream of the heating station 18 and upstream of the cutting station 23.

The post-curing treatment station 61 is still provided to smooth the outer surface of the continuous grooved filter rod 27 after it has passed out of the heating station 18 to eliminate any hairs that may be present on the filter rod 27 and to give the final discrete filter rods 30 a smoother outer finish.

The post-curing treatment station 61 comprises chamber 62 with an entrance 63 and an exit 64, and a pair of spray nozzles 65 within the chamber 62. In use, as the continuous grooved filter rod 27 passes from out of the heating station 18 and into the post-curing treatment station 61, the spray nozzles 65 spray the outer surface of the filter rod 27 with a liquid coating. As the filter rod 27 exits the post-curing treatment station 61, the liquid coating hardens, forming a thin and smooth layer around the filter rod. The liquid coating may comprise a plasticiser and may comprise triacetate. Alternatively, the coating may comprise a liquid polymer, such as, polypropylene.

Following the post-curing treatment station 61, the filter rod 27 is cut into discrete grooved filter rods 70 at a cutting station 23 as per the first and second embodiments of the apparatus 10 of the invention described previously.

Figure 7 shows a cross-section of a third embodiment of the filter rod 70 of the invention made by the third embodiment of the apparatus 60 described above. The filter rod 70 includes a plurality of continuous open grooves 71 on its outer surface extending in an axial direction of the filter rod 70, and a thin smooth outer coating 72 formed by the hardened coating sprayed onto the filter rod 27 as described above. Figure 8 shows one exemplary configuration of a smoking article 8o incorporating a filter 30, 50, 70 of the invention. The smoking article comprises a tobacco rod 81 with a filter 30, 50, 70 of the invention abutting one end of the tobacco rod 81 and joined to the tobacco rod 81 by a tipping wrapper 82 which overlies the join between the tobacco rod 81 and the a filter 30, 50, 70. In the exemplary smoking article 80, ventilation holes 83 are provided to allow ambient air to be drawn into the grooves 31, 51, 71 for increased ventilation as a user draws on the smoking article. Filter rods 30, 50, 70 of the invention may be used in alternative configurations of smoking article other than that shown in Figure 8. For example, the smoking article may comprise a rotatable mouthpiece section which may be provided with a ratchet or pawl to create a tactile and audible click as the mouthpiece portion is rotated. An advantage of the filter rods 50, 70 of the second and third embodiments for use in such a smoking article is that the smooth outer coating 52, 72 provides a harder surface against which such ratchet may engage, making definition of rotational positions more secure and providing improved sensory feedback during rotation, namely more audible clicks and more pronounced tactile sensation. The apparatuses 10, 40, 60 of the invention show the projecting elements 17 being formed in a die. The die 15 may be removable from the apparatus 10, 40, 60 which is advantageous for maintenance and cleaning, but also allows dies with different configurations of projecting elements to be interchanged on the apparatus 10, 40, 60 to enable filter rods with different configurations of grooves to be manufactured. For example, the number of grooves may be varied, as well as the depth or shape, for example squared, V-shaped, U-shaped, etc.

The apparatuses 10, 40, 60 of the invention shown in figures 1, 4 and 6 all comprise separate heating stations 18 adjacent the outlet 13 of the duct 11. Although shown spaced from the outlet 13, the heating stations 18 may be in abutment with the duct 11. However, in addition to these configurations, the invention is intended to incorporate filter rod forming apparatuses in which the heating station is formed integrally with the duct. Such a fourth embodiment of an apparatus 90 of the invention is shown schematically in figure 9 and comprises a duct 91 having an inlet 92 and an outlet 93. The duct 91 comprises a first section 91a that narrows from the inlet 92 to an intermediate point 95, and a second section 91b of constant cross-section extending from the intermediate point 95 to the outlet 93. A source of compressed air is provided to the duct 91 via a compressed air port 94 which, in use, propels filter tow material 25 into and through the duct 91. The second section 91b of the duct 91 has a cross-sectional shape similar to that of the die 15 of the previous embodiments of apparatus, and is the shown in figure 10. The second section 91b of the duct 91 has a central bore 96 and a plurality of projecting elements 97 which project inwardly from the inner wall of the duct 91. The cross- section of the duct 91 with the projecting elements 97 is uniform along the length of the second section 91b.

A difference of the apparatus 90 of the fourth embodiment over those of the previous embodiments is that there is no separate heating station to the duct 91, but instead a different configuration of filter rod heating region is provided, in the form of a heating zone 97 is provided in combination with and around the second duct section 91b. The heating zone 97 comprises a closed chamber 98 around the second duct section 91b with steam inlets 99, 100. The second duct section 91b includes a plurality of steam vents 101 which, in use, allow steam provided to the chamber 98 to pass into the hollow bore 96 of the second duct section 91b. A source of dry steam (not shown) is connected to the steam inlets 99, 100 to supply hot dry steam to the chamber 98.

As with the previous embodiments, a cutting station 23 is provided downstream of the outlet 93 of the duct 91 and includes a cutting blade 24. In use, filter tow material 25, such as cellulose acetate tow mixed with a plasticiser is fed into the inlet 92 of the duct 91 and is conveyed through the first duct section 91a by jets of compressed air provided through the compressed air port 94, and is compressed into a cylindrical rod 26 as it passes through the tapering first duct section 91a. As the cylindrical filter rod 26 is conveyed through the second duct section 91b, the projecting elements 97 form continuous grooves in its outer surface extending in an axial direction of the continuous filter rod 26.

As the filter rod 26 passes through the second duct section 91b, steam supplied to the chamber 98 passes into the filter rod 26 through the steam vents 101 and permeates and heats the filter rod 26. The filter rod 26 is also heated by being in contact with the heated second duct section 91b. The supplied heat cures the plasticiser in the filter tow material 25 so that the continuous grooved filter rod 26 hardens to form a stiff continuous grooved filter rod 27 which exits the heating zone through the outlet 93 of the duct. The stiff continuous grooved filter rod 27 subsequently passes to the cutting station 23 where it is cut into individual lengths of discrete grooved filter rods 30 as described previously.

It is intended within the scope of the invention that the alternative configuration of the apparatus 90 of the fourth embodiment may be combined with the post-treatment stations 41, 61 of either the apparatuses of the second and third embodiments to smooth the outer surface of the stiff filter rod 27.

In the apparatuses 10, 40, 60 of the invention shown in figures 1, 4 and 6, the passage 19 within the chamber 20 of the heating station 18 is configured with a cross-section corresponding to that of the die 15, namely it comprises a plurality of inwardly projecting elements along most or all of its length. Therefore, the cross-section along the line X' - X' in figures 1, 4 and 6 would be the same as the cross-sectional view shown in figure 2. Similarly, the central passage 42 of the post-curing station 41 of the apparatus 40 of figure 4 is also configured with a cross-section corresponding to that of the die 15, namely it comprises a plurality of inwardly projecting elements along most or all of its length. Therefore, the cross-section along the line X" - X" in figure 4 would be the same as the cross-sectional view shown in figure 2.

The advantage of having the passage 19 of the heating station, and also the second duct section 91b of the fourth embodiment 90, formed with inwardly projecting elements is that the projecting elements support and hold the filter rod 26 in the desired grooved configuration as the supplied heat cures the plasticiser. In addition, the inwardly projecting elements of the passage 42 of the post-curing station 41 of the apparatus of figure 4 support the filter rod 26 as the heat smoothes the outer surface of the rod and avoids the filter rod 26 from collapsing or sagging, or the defined grooved shape from altering under the effects of the heat as the plasticiser is melted.

Although figures 2 and 10 show projecting elements 17, 97 spaced from the outer surface of the filter rod 26, these are schematic figures only and the projecting elements 17, 97 would actually be in contact with the filter rod 26. In the case of the passage 42 of the post-curing station 41 of the apparatus of figure 4, the projecting elements being in contact with the filter rod helps conduct heat from the heating elements 43 directly into the filter rod 26 whilst also physically flattening any upstanding hairs on the filter rod.

In the apparatus 40 of the second embodiment, the electrical heating elements 43 are described above as heating the filter rod 27 such that the tow material and plasticiser of the outermost surface of the filter rod 27 melts, and/ or also melting any fine hairs upstanding on the outermost surface of the filter rod 26. However, the invention is not limited to this configuration and method of operation, and the apparatus maybe configured and operated such that the heating elements 43 do not appreciably melt the plasticiser in the outer surface of the filter rod 26, but only soften and physically flatten any upstanding hairs on the filter rod, acting with an "ironing" effect. In such a method of operation, there would not be an appreciable solidified coating formed on the outer surface of the filter rod by melted and hardened tow and plasticiser. However, the final filter rod would have a smoothed outer surface. In such a method of operation, the temperature of the heating elements 43 may be controlled to be below a temperature that would melt the plasticiser in the filter rod 26, for a given conveyance speed of the filter rod 26 though the post-curing treatment station 41.

Although the apparatuses 10, 40, 60 of the first to third embodiments comprise a heating station 18 with a chamber 20 having a steam inlet pipe 21 and an outlet pipe 22, the invention is not limited to this configuration and instead, only an inlet pipe 21 may be provided, or the second pipe 22 may be a second inlet pipe. In such an embodiment, steam would be provided to the chamber and would permeate into the filter rod 26 to heat the filter rod 26, and would be carried out of the chamber 20 within the rod 26, and/ or by seepage between the rod 26 and the wall of the passage 19 of the heating station 18.

As an alternative to a removable die 15, the invention is intended to encompass configurations of apparatus in which the die is not removable from the duct 11 of the apparatus 10, 40, 60. The die 15 may be integrally formed with the duct 11.

The arrangement of grooves 31, 51, 71 around the filters 30, 50, 70 of the invention may vary and maybe regularly sized and/or spaced around the circumference of the filter, as shown in the figures. Alternatively, the grooves may be unevenly spaced or sized, by appropriate configuration of the projecting elements 17 of the die 15. An advantage of having regularly spaced and sized grooves is that the orientation of the filter rod about its axis A-A is not critical in a subsequent smoking article manufacturing process, such as when making ratchet filter smoking articles as described above.

The apparatuses 10, 40, 60 and the methods of the invention achieve manufacture of filter rods without use of a conventional garniture belt and plug wrap, thereby avoiding the added complexity and materials, and therefore cost of conventional methods of wrapped filter manufacture.

As used herein, the term "smoking article" includes smokeable products such as cigarettes, cigars and cigarillos whether based on tobacco, tobacco derivatives, expanded tobacco, reconstituted tobacco or tobacco substitutes and also heat-not-burn products and other nicotine delivery product such as aerosol generation devices including e-cigarettes. The smoking article may be provided with a filter for the gaseous flow drawn by the smoker.

In order to address various issues and advance the art, the entirety of this disclosure shows by way of illustration various embodiments in which the claimed invention(s) may be practiced and provide for superior filters, and apparatuses and methods for manufacture of filters. The advantages and features of the disclosure are of a representative sample of embodiments only, and are not exhaustive and/ or exclusive. They are presented only to assist in understanding and teach the claimed features. It is to be understood that advantages, embodiments, examples, functions, features, structures, and/or other aspects of the disclosure are not to be considered limitations on the disclosure as defined by the claims or limitations on equivalents to the claims, and that other embodiments may be utilised and modifications may be made without departing from the scope and/ or spirit of the disclosure. Various embodiments may suitably comprise, consist of, or consist essentially of, various combinations of the disclosed elements, components, features, parts, steps, means, etc. In addition, the disclosure includes other inventions not presently claimed, but which may be claimed in future.

Claims

A filter for a smoking article comprising an extruded rod of filter material wherein the outer surface of the filter rod comprises a plurality of continuous open grooves extending in an axial direction of the rod.

A filter according to claim l comprising a discrete filter element cut from a continuous extruded rod.

A filter according to claim 2 comprising a single-length filter element for combining with a tobacco rod to make a single smoking article.

A filter according to any preceding claim wherein the filter material comprises cellulose acetate tow which is hardened with a plasticiser to provide a stiff filter.

A filter according to any preceding claim wherein the filter does not comprise any outer wrap around the rod of filter material.

A filter according to any preceding claim wherein the grooves are of uniform size and regularly spaced around the circumference of the filter rod.

A smoking article comprising a tobacco rod and a filter according to any preceding claim joined to one end of the tobacco rod.

An apparatus for manufacturing extruded filters for smoking articles having continuous open grooves extending in an axial direction of the filter on an outer surface of the filter, the apparatus comprising a duct having an inlet and an outlet, the duct tapering between the inlet and the outlet such that loose filter material and plasticiser fed into the inlet is compressed as it is conveyed through the duct into a rod which is expelled from the outlet, wherein the duct is provided with a plurality of inwardly projecting elements to form grooves into the outer surface of the rod of filter material, the apparatus further comprising a heating region to cure plasticiser entrained with the filter material and thereby harden the grooved filter rod.

An apparatus according to claim 8 further comprising a source of compressed air associated with the duct configured to propel filter material fed into the inlet though the duct to and out of the outlet.

An apparatus according to claim 8 or claim 9 wherein the heating region comprises a steam supply to heat and harden the filter material and plasticiser.

An apparatus according to any of claims 8 to 10 wherein the inwardly projecting elements are of a uniform size and are regularly spaced around the duct.

An apparatus according to any of claims 8 to 11 wherein the duct comprises a die on which the inwardly projecting elements are formed.

An apparatus according to claim 12 wherein the die is detachable from the duct.

An apparatus according to any of claims 8 to 13 further comprising a post- curing treatment station downstream of the heating region with respect to the conveyance direction of the extruded filter rod, the post-curing treatment station configured to provide the extruded filter rod with a smoother outer surface than the surface texture present when expelled from the heating station.

An apparatus according to claim 14 wherein the post-curing treatment station comprises an electrical heater configured to heat the outer surface of the filter rod sufficiently.

An apparatus according to claim 15 wherein the electrical heater is configured to heat the outer surface of the filter rod to between 100 - 200 degrees Celsius.

An apparatus according to claim 15 or claim 16 wherein the post-curing treatment station is configured to melt the plasticiser on the outer surface of the filter rod so that the melted outer surface can subsequently set as a smooth finish.

18. An apparatus according to claim 14 wherein the post-curing treatment station comprises a spray-coating station including a spray nozzle and a source of liquid treatment connected to the spray nozzle to spray the liquid treatment onto the outer surface of the filter rod to form a smooth outer coating.

19. An apparatus according to claim 18 wherein the liquid treatment sprayed from the spray nozzle comprises a plasticiser, and may comprise triacetate.

20. An apparatus according to any of claims 8 to 19 further comprising a cutting station configured to cut the continuous extruded filter rod into discrete filter rods having continuous open grooves on their outer surface.

21. A method of manufacturing extruded filters for smoking articles having continuous open grooves extending in an axial direction of the filter on an outer surface of the filter, the method comprising feeding loose filter tow material entrained with a plasticiser into an inlet of a duct, the duct tapering between the inlet and an outlet, conveying the filter tow material through the duct such that it is compressed into a rod which is expelled from the outlet, forming grooves in the outer surface of the rod of filter material by means of a plurality of inwardly projecting elements formed in the duct, and heating the extruded filter rod at a heating region to cure plasticiser entrained with the filter material and thereby harden the grooved filter rod.

22. A method according to claim 21 further comprising propelling the filter tow material fed into the inlet though the duct and out of the outlet using a source of compressed air fed into the duct.

23. A method according to claim 21 or claim 22 comprising heating and

hardening the filter material and plasticiser in the heating region of the apparatus using steam.

24. A method according to any of claims 21 to 23 comprising forming the grooves a uniform size and regularly spaced around the filter rod.

A method according to any of claims 21 to 24 further comprising performing a post-curing treatment on the extruded filter rod to provide the extruded filter rod with a smoother outer surface than the surface texture present when expelled from the heating region.

A method according to claim 25 wherein the post-curing treatment comprises heating the outer surface of the filter rod with an electrical heater and smoothing the outer surface.

A method according to claim 26 wherein the post-curing treatment comprises heating the outer surface sufficiently to melt the plasticiser on the outer surface of the filter rod and subsequently setting the melted outer surface as a smooth finish.

A method according to claim 27 comprising heating the outer surface of the filter rod to between 100 - 200 degrees Celsius.

A method according to claim 25 wherein the post-curing treatment comprises spray-coating a liquid treatment onto the outer surface of the filter rod to form a smooth outer coating.

30. A method according to claim 29 comprising spraying a plasticiser, which may comprise triacetate, onto the outer surface of the filter rod.

31· A method according to any of claims 20 to 28 further comprising cutting the continuous extruded filter rod into discrete filter rods having continuous open grooves on their outer surface.