WO2016075227A1

WO2016075227A1 - Method of manufacturing a filter element for a smoking article

Info

Publication number: WO2016075227A1
Application number: PCT/EP2015/076421
Authority: WO
Inventors: Peter UHRMEISTER
Original assignee: Jt International S.A.
Priority date: 2014-11-12
Filing date: 2015-11-12
Publication date: 2016-05-19
Also published as: EP3217814B1; PL3217814T3; EA201791026A1; JP6718869B2; EP3217814A1; EA037414B1; JP2017533720A

Abstract

The present invention provides a method of manufacturing a filter element (7) for an aerosol generating product (1), and especially a filter plug element (7) for a smoking article, comprising the steps : processing bulk filter material (8) to provide or form a substantially continuous strand (D) of the filter material (8); covering or wrapping the substantially continuous strand (D) of the filter material (8) with at least one layer (9) of sheet material to form a continuous filter rod (R), and forming perforations or holes (17) in the layer (9) of sheet material which covers the continuous filter rod (R) before and/or after the covering or wrapping step.

Description

Method of Manufacturing a Filter Element

for a Smoking Article

The present invention relates to a method of manufacturing or making a filter element for an aerosol generating product, such as a cigarette, a cigarillo, a cigar or the like, which for the sake of brevity will be generally referred to herein simply as a "smoking article". The invention also relates to a filter element obtained or manufactured by the inventive method, as well as an aerosol generating product, such as a smoking article, that includes such a filter element.

As will be appreciated, smoking articles such as cigarettes, cigarillos, cigars and the like are configured to generate an aerosol in the form of smoke for use by a consumer. For this reason, a smoking article is also more generally referred to as an "aerosol generating product" in this disclosure.

In the tobacco processing industry techniques are continually being developed for enhancing the production and performance of cigarettes and other smoking articles. For example, it is a continual goal of the industry to improve the manufacturing efficiency to lower costs and/or to increase productivity. Similarly, it is also a continual goal to improve the product itself from a point of view of consumer use. In view of the above, therefore, an object of this invention is to provide a new and/or improved method of manufacturing a filter element for an aerosol generating product, especially a smoking article, for the tobacco processing industry. In accordance with the invention, a method of manufacturing or making a filter element for an aerosol generating product, such as a smoking article, as recited in claim 1 is provided. Advantageous and/or preferred features of the invention are recited in the dependent claims and are described below.

According to one aspect, therefore, the invention provides a method of manufacturing or producing a filter element for an aerosol generating product, especially a filter plug element for a smoking article, comprising the steps:

processing bulk filter material to provide or form a substantially continuous strand of the filter material;

covering or wrapping the substantially continuous strand of the filter material with at least one layer of sheet material to form an elongate filter member, and

forming perforations or holes in the elongate filter member before and/or after the step of covering or wrapping the strand of filter material. In this way, the invention provides a new and improved method or technique for forming or introducing holes or perforations in a filter element or filter "plug" of a smoking article. The perforations or holes formed in filter element or filter plug of a smoking article provide ventilation enabling air to be drawn laterally into the filter element and, thus, into a main flow or mainstream flow of the aerosol (e.g. smoke) that originates, in use, from an aerosol generating material (e.g. tobacco) of the smoking article. The lateral airflow mixes with the main axial flow of aerosol/smoke through the filter and causes more turbulence than laminar flow. This can result in increased filtration efficiency, and/or an easier pressure drop adjustment for the filter element. In the event that one or more flavour and/or indicator elements are provided in the filter plug or filter element, the airflow generated by the perforations or holes can produce a higher interaction or pick-up rate of flavour in the filter element by the mainstream smoke. Also, the perforations or holes can provide a capillary effect to distribute a flavouring liquid or an indicator liquid faster, thereby providing a faster or more efficient and homogeneous release of taste components to the mainstream aerosol/smoke. By forming the perforations or holes in the filter elements prior to manufacture or assembly of the smoking articles themselves, e.g. during the manufacture or production of the filter elements, the visibility of such perforations or holes otherwise formed through the outside of smoking articles and considered unsightly can be minimised and largely avoided.

In a preferred embodiment, the step of forming perforations or holes comprises forming those perforations or holes in the layer of sheet material that covers or wraps the elongate filter member. Where the step of forming the perforations or holes is performed or carried out after the step of covering or wrapping the strand of filter material with the layer of sheet material, the perforations or holes are preferably not only formed through the layer of sheet material, but also into or through the filter material covered or wrapped by the at least one layer of sheet material. This not only ensures a good flow path for lateral airflow into the mainstream flow of smoke through the filter material, it also enhances the capillary effect for better distributing a flavouring liquid or an indicator liquid through the filter material.

In a preferred embodiment, each discrete or individual filter element is formed as a rod element or plug element of filter material, such as cellulose acetate tow or fibres, and is covered or wrapped or enclosed by at least one layer of sheet material, known as "plug wrap". This sheet material may be porous (e.g. paper) or non-porous (e.g. a plastic film or coated paper) . Thus, the step of forming perforations or holes in the rod element of filter material then preferably comprises forming the perforations or holes in the at least one layer of sheet material, i.e. in the plug wrap, such that they communicate with the axial or mainstream flow of aerosol/smoke through the filter material within or enclosed by the plug wrap. The individual filter rod elements or plug elements are typically produced by fabricating a continuous or long filter member and then cutting that elongate filter member into a plurality of shorter elements, each typically of uniform length. The fabrication of the continuous or long filter rod prior to cutting therefore preferably includes the step of forming a plurality of perforations or holes in the at least one layer of sheet material or plug wrap which is wrapped around and/or encloses the filter material, e.g. cellulose acetate tow or fibres, of the continuous or long filter rod. The discrete or individual plug elements or rod elements of filter material may then be subsequently cut from the elongate filter member.

The maintenance of tar, nicotine, and carbon monoxide (TNCO) levels with perforated tipping paper and plug wrap can be difficult. In particular, porosity change of tipping paper requires a long lead-time, which can generate write-off costs with old tipping paper stock. Furthermore, a change in the plug wrap or the pressure drop of the filter over time can also impact on cost, with inventory options for the plug wrap limited as well. The method of the invention addresses these issues with the potential to vary the number of perforations or holes and their respective depths to imitate variation in porosity of the plug wrap at constant cost . In this way, the ventilation of the filter element or plug can be varied with constant tipping paper porosity over a sufficient range for maintenance of the TNCO levels, thereby reducing the tipping paper inventories and write-offs.

In one preferred embodiment, the sheet material or plug wrap that covers or wraps the elongate filter member may be pre- perforated. In other words, the sheet material is perforated prior to the step of covering or wrapping the substantially continuous strand of filter material therewith.

In a preferred embodiment of the invention, the elongate filter member comprises either a generally continuous filter rod or a filter rod member of a predetermined length, and the method comprises: cutting the continuous filter rod or the filter rod member of predetermined length into a plurality of discrete or individual filter elements, with each discrete or individual filter element being configured for assembly with a respective tobacco rod element to form a smoking article. In this embodiment, the step of forming the perforations or holes in the layer of sheet material is performed or carried out before this cutting step. Accordingly, each discrete or individual filter element for an individual smoking article already has the perforations or holes for ventilation when it is produced or manufactured.

In a particularly preferred embodiment, the elongate filter member is a generally continuous filter rod and the method includes: cutting the continuous filter rod into a plurality of elongate rod members of a predetermined length. The step of forming the perforations or holes in the layer of sheet material or plug wrap that covers or wraps the strand of the filter material is then preferably carried out or performed on the elongate rod members of predetermined length. It will be noted, however, that the step of forming the perforations or holes in the layer of sheet material or plug wrap that covers or encloses the strand of the filter material may alternatively be carried out or performed on the continuous filter rod.

In a preferred embodiment of the invention, the perforations or holes are formed and/or arranged randomly in the layer of sheet material or plug wrap that covers or wraps the strand of the filter material. Alternatively, or in addition, the perforations or holes may be formed or arranged evenly or in an ordered arrangement in the layer of sheet material or plug wrap that covers or wraps the strand of the filter material. Preferably, the perforations or holes are distributed and/or formed around a periphery or circumference of the elongate filter member. Furthermore, the perforations or holes may be formed and/or distributed along a longitudinal extent of the elongate filter member.

In a preferred embodiment, the step of forming perforations or holes in the layer of sheet material or plug wrap that covers or wraps the strand of the filter material includes moving the elongate filter member relative to a perforating device or hole forming device; e.g. rotating the elongate filter member about a longitudinal axis thereof. Preferably, the perforating device or the hole forming device comprises at least one laser beam from a laser source, such as a pulsed or a continuous laser source, and more preferably multiple laser beams. Thus, the perforations or holes may be formed by means of at least one laser beam, which may ablate or cut and then penetrate or perforate the at least one layer of sheet material or plug wrap for communication with the mainstream flow through the filter material. By controlling the laser settings, round or cylindrical holes can be created having a minimum or predetermined small diameter and a controllable depth. The at least one laser beam is typically movable with respect to the element of filter material; for example, along a longitudinal direction and/or in a transverse direction with respect to the elongate filter member. By virtue of such relative movement, it becomes possible to generate a range of different patterns for the perforations or holes formed in the filter element.

In a preferred embodiment, the perforating device or hole forming device may include a beam splitter arrangement for generating multiple laser beams from a single laser source {e.g. a continuous or a pulsed laser source). In this regard, the beam splitter arrangement may include a prism and/or one or more mirrors. The beam splitter arrangement may preferably comprise a plurality of optical fibres to convey and direct respective individual laser beams towards the filter element from the laser source. Optical fibres are highly flexible and relatively inexpensive, and are therefore very practical for transmitting multiple laser beams. The ends of the optical fibres can be arranged in a predetermined array or pattern for transmitting the laser beams onto the elongate filter member. The optical fibres for the multiple laser beams are therefore preferably directed towards and arranged around and/or along a length or extent of the elongate filter member for simultaneously forming a plurality of spaced perforations or holes in the filter member.

In a particularly preferred embodiment, the beam splitter arrangement includes an optical fibre support configured to receive and hold a free end of each of the optical fibres in such a way that the laser beam from each individual optical fibre is directed towards the longitudinal axis of the filter element. Thus, the optical fibre support may be configured to hold the optical fibres such that the laser beams are emitted therefrom in a plane generally perpendicular to a length or longitudinal axis of the element of filter material. This perpendicular orientation of the laser beams to the filter element thus forms straight cylindrical holes. Alternatively, or in addition, the optical fibre support may be configured to hold the optical fibres in such a way that the laser beams are emitted from the optical fibres to define a generatrix of a conical surface having its vertex on the longitudinal axis of the elongate filter member. With such an angled or oblique orientation of the laser beams to the filter member, inclined holes are formed.

According to another aspect, the present invention provides a filter element for an aerosol generating product, especially a filter plug element for a smoking article, manufactured or obtained by a method according to any one of the embodiments described above .

According to a further aspect, the present invention provides an aerosol generating product, especially a smoking article, comprising: an elongate rod element of an aerosol generating material, e.g. a tobacco rod, assembled with a filter element of the invention as described above. In a preferred embodiment, the elongate element of an aerosol generating material is assembled with the filter element by arranging an end of the filter element (e.g. plug element) adjacent and/or abutting an end of the elongate element of aerosol generating material (e.g. tobacco rod element) , and joining or fastening those elements together via at least one layer of sheet material or wrapper that covers or wraps the said elements at least in a region of their abutting ends. This at least one layer of sheet material or wrapper that joins or fastens the said elements together in the assembling step typically comprises paper, known as "tipping paper", although other materials may be contemplated. Because the filter element is perforated before assembly with the tobacco rod to form the smoking article, it also becomes possible to employ pre-perforated tipping paper with few perforations or holes which are barely visible or apparent to a consumer without a close inspection. This way, it becomes possible to eliminate formation of perforations or holes simultaneously through both the tipping paper and the plug wrap from the method of manufacturing the smoking article.

For a more complete understanding of the invention and the advantages thereof, exemplary embodiments of the invention are explained in more detail in the following description with reference to the accompanying drawing figures, in which like reference characters designate like parts and in which:

Fig. 1 is a schematic perspective view of a construction of a smoking article (e.g. cigarette) obtained by a method according to a preferred embodiment;

Fig. 2 is a schematic perspective view of a smoking article (e.g. cigarette) manufactured by a method according to a preferred embodiment; Fig. 3 is a schematic side view of a production system for making a filter rod for use in manufacturing a smoking article ,-

Fig . 4 is a schematic side view of a filter rod produced for use in a method according to an embodiment of the invention;

Fig. 5 is a schematic side view of another filter rod for use in a method according to an embodiment of the invention; and

Fig. 6 is a flow diagram that schematically represents a method of an embodiment of the invention.

The accompanying drawings are included to provide a further understanding of the present invention and are incorporated in and constitute a part of this specification. The drawings illustrate particular embodiments of the invention and together with the description serve to explain the principles of the invention. Other embodiments of the invention and many of the attendant advantages of the invention will be readily appreciated as they become better understood with reference to the following detailed description.

It will be appreciated that common and/or well understood elements that may be useful or necessary in a commercially feasible embodiment are not necessarily depicted in order to facilitate a more abstracted view of the embodiments. The elements of the drawings are not necessarily illustrated to scale relative to each other. It will further be appreciated that certain actions and/or steps in an embodiment of a method may be described or depicted in a particular order of occurrences while those skilled in the art will understand that such specificity with respect to sequence is not actually required. It will also be understood that the terms and expressions used in the present specification have the ordinary meaning as is accorded to such terms and expressions with respect to their corresponding respective areas of inquiry and study, except where specific meanings have otherwise been set forth herein. With reference to Figs. 1 and 2 of the drawings, the basic structure or construction of a smoking article 1 - in this case, a cigarette - according to a preferred embodiment is illustrated schematically. The smoking article 1 comprises an elongate, generally cylindrical rod element 2 of an aerosol generating material 3, especially a smoking material, such as tobacco, which is covered or wrapped with a layer 4 of sheet material in the form of cigarette paper. The layer or sheet 4 of cigarette paper is typically fixed around the body or mass of tobacco 3 via at least one fine line 5 of adhesive or glue applied in an overlap region 6 of the cigarette paper. In addition to rod element 2 of tobacco 3, the smoking article 1 comprises an elongate, generally cylindrical filter rod element or plug element 7 of a filter material 8, such as cellulose acetate tow, which is covered or wrapped with a layer 9 of sheet material commonly referred to as plug wrap. Again, the layer or sheet 9 of plug wrap is typically fixed around the body of filter material 8 via adhesive or glue 10 applied in an overlap region 11 of the plug wrap 9. Where the filter rod element or plug element 7 includes a breakable capsule of flavouring liquid and/or taste altering liquid embedded in the filter material 8, the sheet 9 of plug wrap may be selected to be non-porous to prevent uncontrolled transport or seepage of the liquid there-through . During fabrication or manufacture of the cigarette 1, the rod element 2 of tobacco 3 and the plug element 7 of filter material 8 are arranged substantially in alignment such that an end 12 of the tobacco rod element 2 is adjacent to and/or in abutment with an end 13 of the filter plug element 7. One or more layer 14 of a paper sheet or wrapper, commonly known as tipping paper, is then used to join or fasten the tobacco rod element 2 and the filter plug element 7 together. In this regard, the layer 14 of tipping paper covers or wraps those elements 2, 7 in a region of their abutting ends 12, 13 and is fixed to each of the tobacco rod element 2 and the filter plug element 7 via a fine line 15 of adhesive or glue applied along an edge region 16 of the layer 14. The layer or sheet 14 of tipping paper typically fully covers the filter plug element 7, as seen in Fig. 1.

Referring further to Fig. 1, it can be seen that according to the method of fabrication or manufacture of the cigarette 1, both the plug of filter material 8 and the layer 9 of sheet material or plug wrap around the filter material 8 of the filter plug element 7 have an ordered array of perforations or holes 17 formed therein before the tobacco rod element 2 and the filter plug element 7 are assembled and joined together with the layer or sheet 14 of tipping paper. Although the layer 9 of plug wrap can be seen to include the perforations or holes 17 before the layer 9 is wrapped around the cylindrical body of filter material 8, this view simply illustrates the construction of the filter element 7 and need not necessarily be the case. In practice, the perforations or holes 17 may also be formed in the layer 9 of plug wrap after that layer 9 has been wrapped and fixed around the body of filter material 8 during fabrication of the plug element 7. As seen in Fig. 1, the perforations or holes 17 are formed or arranged in rows which extend around a circumference of the filter plug element 7 in a central region thereof. Because the layer 9 of plug wrap in the filter plug element 7 is already perforated with holes 17 when that filter element 7 is combined and assembled with the tobacco rod element 2, it is possible to use a pre-perforated layer 14 of tipping paper when joining or fastening those two elements 2, 7 of the cigarette 1. In this regard, the pre-perforated layer 14 of tipping paper will usually have a relatively small number of perforations or holes 18 so that these are not visible or apparent to a consumer without very close inspection. These perforations or holes 18 in the layer 14 of tipping paper are nevertheless sufficient to allow a lateral influx of air into the filter plug element 7 through the perforations or holes 17 in the layer 9 of plug wrap. By employing pre-perforated tipping paper, it is also possible to eliminate the need to form perforations or holes through both the tipping paper and the plug wrap simultaneously from the method of manufacturing the smoking article. As can be seen in Fig. 2, the layer 14 of tipping paper effectively hides or obscures the holes or perforations 17 in the layer 9 of plug wrap and only a single fine row or line of perforations or holes 18 is visible on close inspection by a consumer. When a consumer draws on a proximal end of the filter element 7 in use, an axial flow or mainstream flow 19 of an aerosol or smoke S from the tobacco 3 is drawn longitudinally of and within the smoking article 1 and through the filter element 7 (i.e. in a direction of the arrow) . At the same time, an air- flow is also drawn laterally through the perforations or holes 17, 18 and this lateral air flow mixes with the mainstream flow 19 to create turbulence and a more convoluted flow path through the filter element 7. With reference to Figs. 3 to 5 of the drawings, the step of forming the perforations or holes 17 in the filter element 7, and particularly in the plug of filter material 8 and the layer 9 of sheet material or plug wrap around the filter material 8, may be performed during fabrication of the filter element 7. In this regard, the discrete or individual filter rod elements 7 are cut from a continuous filter rod R or from long filter rod members 20 (e.g. as shown schematically in Figs. 4 and 5) which are typically fabricated or produced in a dedicated filter making apparatus or machine 30 shown schematically in Fig. 3 of the drawings for manufacture of standard crimped cellulose acetate filters commonly used in the tobacco industry. It should be noted, however, that the step of perforating holes in the filter plug element 7, and especially in the layer 9 of plug wrap, could likewise be implemented in filter rod elements 7 produced with randomly oriented fibres of cellulose acetate, such as obtained from TURMALIN filter maker from the German manufacturer HAUNI .

In a first stage A of the filter making procedure, the filter material 8, comprising cellulose acetate tow, is treated and prepared. Firstly, the filter tow 8 is drawn in a generally continuous strand or ribbon D from a bulk supply 8 ' , such as bale, and then conveyed through a series of banding jets 31, 31', 31", pre-tension rollers 32, and a blooming roller 33. In this first phase A, the filter tow 8 is stretched and relaxed to create a maximum surface area in the fibres of the cellulose acetate. In a second stage B of the filter making procedure, the generally continuous strand or ribbon D of filter tow 8 passes through a plasticiser addition unit 34, in which a plasticiser such as a triacetin is added to the fibres (e.g. by spraying) to enhance their adhesion together. At an exit of the plasticiser addition unit 34, the filter tow 8 passes through delivery rollers 35 into a third, rod- making stage C of the filter making procedure. At this position, the strand of filter tow fibres 8 is channelled via a guide device 36, especially a trumpet guide having a so- called "stuffer jet" or transport jet 36", to form or provide the substantially continuous strand D of filter tow material

8 with the desired circular cross-sectional shape. At this stage, a capsule, pellet or thread of flavouring material (with or without indicator) may also be introduced into the strand D of filter material 8. At the same time, a sheet or layer 9 of plug wrap material is drawn from a bulk roll 37 and fed via rollers up to the tow fibre strand D. An adhesive is typically applied to the layer 9 of plug wrap material via an applicator nozzle 38 as that layer 9 of plug wrap material is brought into contact with and wrapped around the strand of filter material 8. This adhesive, which usually bonds or fixes the plug wrap 9 to the filter material 8, may be applied to the plug wrap material 9 as a single line or as multiple lines of adhesive, and may follow either straight or non- linear application patterns (circular, wavy or curly, for example) . To seal the plug wrap 9 over or around the rod- like strand D of filter material 8 formed in the guide device 36, a seam line 10 of glue is preferably applied to an overlap region 11 of the plug wrap 9 at an outlet of the guide device 36. In some cases, however, such seam lines may be deposited at the same time as the attachment glue at nozzle 38. The continuous filter rod R that is thereby formed comprising the strand D of filter material 8 now covered with the layer

9 of plug wrap then passes through a sealing chamber 39 to seal and bond the wrapped rod R in its final desired shape. The layer 9 of plug wrap sheet material which is wrapped around and covers the filter tow 8 assists in maintaining a desired cylindrical form of the filter rod. Upon emerging from the sealing chamber 39, the continuous rod R of filter material 8 is inspected at an inspection station 41 and then conveyed to a cutting station 42 where it is cut into predetermined lengths of rod members 20, e.g. as shown in Figs. 4 and 5, each of which then undergoes a perforating or hole forming step in a hole-forming device 40.

The perforating or hole forming device 40 comprises a laser source for generating a laser beam, and a beam splitter for splitting the single laser beam from the laser into multiple laser beams. The beam splitter of the perforating device 40 includes a plurality of optical fibres, each of which is configured and arranged to convey and direct individual laser beams towards the filter rod members 20. In this regard, the optical fibres are mounted within a support that holds a free end of each of the optical fibres arranged in a row or array directed at and arranged around and/or along an extent of the rod members 20. In this way, the multiple laser beams emitted from the ends of the individual optical fibres are directed towards a longitudinal axis of the filter rod member 20 and can simultaneously cut or burn a plurality of perforations or holes 17 (e.g. preferably evenly spaced) through the layer 9 of plug wrap around the rod members 20. By controlling the laser settings, such as power and operation time, it is also possible to control parameters, e.g. depth, of the holes 17 formed. Indeed, it is desired that the perforations or holes 17 not only penetrate the layer (s) 9 of plug wrap around the filter material 8, but also penetrate through the fibres of the filter tow 8 towards the middle of the rod members 20. The optical fibre support may be movable with respect to the filter rod members 20 to generate the desired constellation of perforations or holes 17, and/or more preferably the filter rod members 20 may be movable with respect to the support; e.g. in the longitudinal direction and/or in rotation about their longitudinal axes.

As seen in Fig. 4, the perforations or holes 17 formed in the filter rod members 20 (and thus in each of filter element 7) may be arranged in a regular or ordered, densely packed array around a circumference of the filter rod member 20 and along a length thereof. In an alternative embodiment in Fig. 5, the perforations or holes 17 formed in the filter rod members 20 may be arranged in series of single circumferential rows 21 evenly spaced apart along the filter rod member 20 such that each filter element 7 cut from the filter rod member 20 has a single circumferential row 21 of those perforations or holes 17. In a further alternative discussed above with respect to Fig. 1, each filter element 7 may include a series of rows 21 of the perforations or holes 17, e.g. circumferentially in a particular region thereof.

The perforations or holes 17, which are formed in the layer or sheet 9 of plug wrap around the tow material 8 and extend into the filter plug elements 7, can act as capillaries or pathways to assist transportation of flavouring liquids from capsules along and through the filter elements 7. They can thus assist the activation of indicators and faster distribution in the filter element 7 for release to the axial or mainstream smoke 19. In addition, lateral air-flow through the perforations or holes 17 causes a more turbulent flow of smoke through the filter element 7 which facilitates pick-up of more flavour molecules into mainstream smoke 19. Forming the perforations or holes 17 in the plug wrap layer 9 is also able to flexibly mimic porous plug wrap material with the number and extent of perforation effectively varying porosity for pre-perforated tipping paper products. After the perforating or hole forming procedure in the hole- forming device 40, the rod members 20 may again be inspected at an inspection station 41 and then conveyed via a conveyor device 43 either to a storage buffer 44 or to another cutting station where the rod members 20 are cut to individual filter elements 7, which are then stored in a storage buffer.

With reference now to Fig. 6 of the drawings, the method of manufacturing a filter plug element 7 for a smoking article 1 according to the invention is illustrated schematically, with the numbered boxes I to IV of the diagram representing steps of the method. In particular, the first box I represents the step of providing a bulk supply 8 ' of a filter material, such as cellulose acetate tow, for processing as shown in Fig. 3. The second box II represents the step of processing the bulk filter material 8 to form a substantially continuous strand D of the filter material 8, which is preferably treated, guided and shaped to have a generally cylindrical cross-section. The third box III of the diagram in Fig. 6 then represents the step of covering (e.g. wrapping) the substantially continuous strand D of the filter material 8 with at least one layer 9 of sheet material or plug wrap to form an elongate filter member, which may be a generally continuous filter rod R or an elongate filter rod member 20 of predetermined length. The fourth box IV represents the step of forming perforations or holes 17 in the layer 9 of sheet material or plug wrap that covers the elongate filter member R, 20 before and/or after the step of covering the strand D of filter material 8. In this regard, the layer 9 of sheet material on the roll 37 may be pre-perforated. Alternatively, or in addition, the step of forming the perforations or holes 17 in the layer 9 of sheet material or plug wrap may be carried out or performed on the elongate filter member R, 20 before it is cut to produce a plurality of the discrete or individual filter elements 7 for individual smoking articles 1.

Although specific embodiments of the invention have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations exist. It should be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration in any way. Rather, the foregoing summary and detailed description will provide those skilled in the art with a convenient road map for implementing at least one exemplary embodiment, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope as set forth in the appended claims and their legal equivalents. Generally, this application is intended to cover any adaptations or variations of the specific embodiments discussed herein. Also, it will be appreciated that in this document, the terms "comprise", "comprising", "include", "including", "contain", "containing", "have", "having", and any variations thereof, are intended to be understood in an inclusive (i.e. nonexclusive) sense, such that the process, method, device, apparatus or system described herein is not limited to those features or parts or elements or steps recited but may include other elements, features, parts or steps not expressly listed or inherent to such process, method, article, or apparatus. Furthermore, the terms "a" and "an" used herein are intended to be understood as meaning one or more unless explicitly stated otherwise. Moreover, the terms "first", "second", "third", etc. are used merely as labels, and are not intended to impose numerical requirements on or to establish a certain ranking of importance of their objects .

List of Reference Signs

1 smoking article

2 elongate element of tobacco or tobacco rod element 3 aerosol generating material or tobacco

4 layer of sheet material or cigarette paper

5 line of adhesive or glue

6 overlap region of cigarette paper

7 elongate element or plug element of filter material 8 filter material or cellulose acetate tow

8¹ supply or bale of filter material

9 layer of sheet material or plug wrap

10 line of adhesive or glue

11 overlap region of plug wrap

12 end of tobacco rod element

13 end of filter plug element

14 layer or sheet of material or tipping paper

15 line of adhesive or glue

16 edge region of the layer or sheet of tipping paper 17 perforation or hole in the layer of plug wrap

18 perforation or hole in the layer of tipping paper

19 axial flow or mainstream flow of aerosol or smoke

20 filter rod member

21 row of holes or perforations

30 filter making apparatus or machine

31 banding jet

31' banding jet

31" banding jet

32 pre- tension roller

33 blooming roller

34 plasticiser addition unit

35 delivery roller

36 guide device or trumpet guide 36· transport jet or "stuffer" jet

37 bulk roll

38 applicator nozzle

39 sealing chamber

40 perforating device or hole-forming device

41 inspection station for rod measurement/inspection

42 cutting station

43 conveyor device for filter elements or rod members

44 storage buffer

S aerosol or smoke

D strand of filter material

R continuous filter rod

Claims

1. A method of manufacturing filter elements (7) for an aerosol generating product (1) , especially filter plug elements (7) for a smoking article, comprising:

processing bulk filter material (8) to provide or form a substantially continuous strand (D) of the filter material (8) ;

covering the substantially continuous strand (D) of filter material (8) with at least one layer (9) of sheet material to form an elongate filter member (R, 20) ; and forming perforations or holes (17) in the elongate filter member (R, 20) before and/or after the step of covering the strand (D) of filter material (8) .

2. A method according to claim 1, wherein the step of forming the perforations or holes (17) comprises forming those perforations or holes (17) in the at least one layer (9) of sheet material that covers or wraps the elongate filter member (R, 20) .

3. A method according to claim 1 or claim 2, wherein the sheet material (37) of the layer (9) is pre-perforated before covering the substantially continuous strand (D) of the filter material (8) therewith.

4. A method according to any one of the preceding claims, wherein the step of forming the perforations or holes (17) is performed after the step of covering or wrapping the strand (D) of filter material (8) with the at least one layer (9) of sheet material, with the perforations or holes (17) preferably being formed not only in the layer (9) of sheet material, but also in or through the filter material (8) covered or wrapped by the at least one layer (9) of sheet material.

5. A method according to any one of the preceding claims, wherein the elongate filter member (R, 20) comprises a substantially continuous filter rod (R) or a filter rod member (20) of predetermined length, and wherein the method comprises: cutting the continuous filter rod (R) or the filter rod member (20) of predetermined length into a plurality of discrete or individual filter elements (7) , each of which is configured to be assembled with a respective rod element (2) of aerosol generating material (3) , such as tobacco, to form a smoking article (1) , wherein the step of forming the perforations or holes (17) in the layer (9) of sheet material is carried out before the cutting step.

6. A method according to any one of the preceding claims, wherein the elongate filter member (R, 20) comprises a continuous filter rod (R) , wherein the method comprises: cutting the continuous filter rod (R) into a plurality of elongate rod members (20) of predetermined length, wherein the step of forming perforations or holes (17) in the layer (9) of sheet material is carried out or performed on the elongate rod members (20) .

7. A method according to any one of the preceding claims, wherein the perforations or holes (17) are formed or arranged randomly in the layer (9) of sheet material, and/or wherein the perforations or holes (17) are formed or arranged evenly or regularly in said layer (9) .

8. A method according to any one of the preceding claims, wherein the perforations or holes (17) are arranged or formed around a circumference of the continuous filter rod (R) or the elongate rod members (20) , and/or wherein the perforations or holes (17) are arranged or formed longitudinally of the continuous filter rod (R) or the elongate rod members (20) .

9. A method according to any one of the preceding claims, wherein the step of forming perforations or holes (17) in the layer (9) of sheet material includes moving the continuous filter rod (R) or the elongate rod members (20) relative to a perforating device or a hole forming device (40) , preferably rotating the filter rod (R) or the elongate rod members (20) about a longitudinal axis thereof .

10. A method according to any one of the preceding claims, wherein the step of forming perforations or holes (17) includes irradiating the layer (9) of sheet material, especially after it covers or wraps the filter material (8) of the filter rod (R) , with at least one laser beam, whereby the perforations or holes (17) are formed by means of the at least one laser beam.

11. A method according to claim 10, wherein the at least one laser beam is movable with respect to the filter rod (R) or filter rod members (20) , preferably movable along a longitudinal direction and/or in a transverse direction with respect thereto.

12. A method according to any one of the preceding claims, wherein a perforating device or hole forming device (40) comprises a laser source, a beam splitter arrangement for generating multiple laser beams from said laser source, a plurality of optical fibres for conveying and directing a respective laser beam towards the filter rod (R) or the filter rod members (20) , and an optical fibre support configured to receive and hold a free end of each of the optical fibres in such a way that the laser beams from each individual optical fibre are arranged adjacent and directed towards the layer (9) of sheet material which covers the filter rod (R) or the filter rod members (20) .

13. A method according to any one of the preceding claims, comprising the step of :

cutting the elongate filter member (R, 20) into a plurality of discrete or individual filter elements (7) , each of which is configured for assembly with an element (2) of aerosol generating material (3), especially a rod element of tobacco;

wherein the filter material (8) comprises cellulose acetate tow and wherein the layer (9) of sheet material is porous or non-porous, preferably comprising paper.

14. A filter element (7) for an aerosol generating product (1) , and especially a filter plug element for a smoking article, manufactured or obtained by a method according to any one of the preceding claims.

15. An aerosol generating product (1) , especially a smoking article, comprising: an elongate element (2) of aerosol generating material (3) , such as tobacco, assembled with a filter element (7) according to claim 14.