WO2017021422A1

WO2017021422A1 - Tobacco smoke filter

Info

Publication number: WO2017021422A1
Application number: PCT/EP2016/068466
Authority: WO
Inventors: Ahmad Fashihul Lisan; Paul Ronald MORRIS
Original assignee: Essentra Filter Products Development Co. Pte. Ltd; Essentra Filter Products Limited
Priority date: 2015-08-03
Filing date: 2016-08-02
Publication date: 2017-02-09
Also published as: CN106387993A; CN106387993B; CN112998312A; CN112998312B

Abstract

A method of producing a (e.g. recess) tobacco smoke filter or filter element comprising the steps of: advancing longitudinally a continuous flow of dual filter rods wherein the dual filter rods in the longitudinally advancing flow are longitudinally spaced from each other, each dual filter rod comprising a longitudinally extending core of tobacco smoke filtering material, and wherein each dual filter rod comprises; a first base rod at a first end of the dual filter rod; a second base rod at a second end of the dual filter rod; and a third base rod positioned longitudinally between the first and second base rods; providing a common wrapper around the continuous flow of dual filter rods to provide a product rod comprising a plurality of wrapped dual filter rods which are longitudinally spaced from each other within the product rod; cutting through the product rod in register with a position half way along a third base rod; and/or cutting through the product rod in register with a position half way along a space between dual filter rods.

Description

TOBACCO SMOKE FILTER

The present invention relates to tobacco smoke filters and filter elements for smoking articles such as cigarettes.

In recent years, there has been a growing commercial interest in the use of "shape filters" i.e. tobacco smoke filters including one or more elements that extend longitudinally of the core of tobacco smoke filtering material (e.g. extending longitudinally through the core of tobacco smoke filtering material; extending longitudinally along the core of tobacco smoke filtering material), such as threads or extruded elements, that are visible at the mouth end of the filter. One advantage of shape filters over standard tobacco smoke filters is that they provide a distinctive mouth end appearance that is useful for branding and anti-counterfeit purposes.

However, there exists a problem that only elements having a symmetrical cross-section can be included in shape filters using existing manufacturing methods. This is because tobacco smoke filters are typically manufactured by a method comprising the steps:

Providing multiple (e.g. dual) filter rods including two longitudinally extending cores of filtering material placed end to end in a mirror image relationship;

attaching a rod of tobacco to each end of the filter rod; and

cutting the dual filter rod halfway along its length to provide two individual cigarettes.

It is possible to use such a method with a dual filter rod which includes an element which is visible at the mouth end of the filter. However, if the cross-sectional shape of the element is asymmetrical then the shapes of the element at the mouth end of the two filters produced by this method will be mirror images of one-another. This is clearly unsatisfactory for branding and anti-counterfeit purposes, because one filter will have the correct image (for example, logo), while the second will have an incorrect image (the mirror image).

Accordingly, there exists a need to provide a method of manufacturing filters / filter elements wherein the mouth end appearance of all filters / filter elements created by the method is identical, even when the element extending longitudinally of the rod has an asymmetric cross-section. (Herein the term "asymmetric", as in e.g. asymmetric cross-section, means reflectively asymmetric.)

The present application provides a new method of manufacturing recess tobacco smoke filters or filter elements that satisfies this need, and provides filters / filter elements which have identical, rather than mirror imaged end appearances, whatever the cross-section of the extruded element. As a result, a much wider variety of element cross-sectional shapes can be used in this method compared to methods previously known in the art, rendering this method exceptionally useful for branding and anti-counterfeit purposes. Recess filters are well known in the tobacco industry. They are typically manufactured by wrapping a continuous stream of filter segments at spaced intervals in a relatively stiff plug wrap paper. By cutting the filter stream in a region where no filter element is present, a recess filter can be obtained - the stiff plugwrap paper providing sufficient rigidity to enable the final cigarette to be manufactured and used without crushing the exposed paper end of the filter. Recess filters provide an additional distinction in end appearance and filter performance.

According to the present invention in a first aspect there is provided a method of manufacturing a (e.g. recess) tobacco smoke filter or filter element;

the method comprising the steps of:

advancing longitudinally a continuous flow of dual filter rods wherein the dual filter rods in the longitudinally advancing flow are longitudinally spaced from each other, each dual filter rod comprising a longitudinally extending core of tobacco smoke filtering material, and wherein each dual filter rod comprises a first base rod at a first end of the dual filter rod; a second base rod at a second end of the dual filter rod; and a third base rod positioned longitudinally between the first and second base rods; providing a common wrapper around the continuous flow of dual filter rods to provide a product rod comprising a plurality of wrapped dual filter rods which are longitudinally spaced from each other within the product rod; cutting through the product rod in register with a position half way along a third base rod; and/or cutting through the product rod in register with a position half way along a space between dual filter rods.

It will be appreciated that by cutting the product rod in register with a position half way along each third base rod, and cutting through the product rod in register with a position half way along each space between dual filter rods, the product rod will be cut into separate recess filters/filter elements for subsequent use. Alternatively, by first cutting the product rod in register with a position half way along a third base rod, and cutting the product rod in register with a position half way along the next third base rod (which is in the next dual filter rod) in the flow, a dual filter product rod will be obtained (see Fig 5a). The dual filter product rod may then be cut in register with a position halfway along the length of the dual filter product rod, to provide two recess filters/filter elements for subsequent use. Often a dual filter product rod will be attached to a tobacco envelope at each end (e.g. by ring tipping) prior to the final cut (in register with a position halfway along the length of the dual filter product rod to which the tobacco envelopes have been attached) to provide two recess filter cigarettes. It will be understood that these methods are all within the aspect of the invention defined above.

The first base rod preferably comprises a first longitudinally extending (e.g. substantially cylindrical) core of tobacco smoke filtering material; and a first element extending longitudinally of the (first) core of tobacco smoke filtering material (e.g. extending longitudinally through the core of tobacco smoke filtering material; extending longitudinally along the core of tobacco smoke filtering material) which is visible at the first end of the dual filter rod. The second base rod preferably comprises a second longitudinally extending (e.g. substantially cylindrical) core of tobacco smoke filtering material; and a second element extending longitudinally of the (second) core of tobacco smoke filtering material (e.g. extending longitudinally through the core of tobacco smoke filtering material; extending longitudinally along the core of tobacco smoke filtering material) which is visible at the second end of the dual filter rod. The cross-section of the first element (extending longitudinally of the first core of tobacco smoke filtering material) visible at the first end of the dual filter rod is preferably a mirror image of the cross-section of the second element (extending longitudinally of the first core of tobacco smoke filtering material) visible at the second end of the dual filter rod. The third base rod preferably comprises a third longitudinally extending (e.g. substantially cylindrical) core of tobacco smoke filter material. The third base rod is preferably a base rod that is well known in the art (e.g. a non- wrapped mono-acetate base rod). The cross-sections of the first and second (longitudinally extending) elements are preferably asymmetric.

The dual filter rod may comprise one or more additional base rods (i.e. a fourth, fifth sixth or greater base rod) positioned longitudinally between the first and second base rods.

It will be appreciated that this method produces two tobacco smoke filters / filter elements that have an identical mouthpiece appearance, even when the longitudinally extending element has an asymmetric cross-section. As best seen in Figures 5a, 7 and 8, the method may provide a dual filter product rod. In subsequent filter cigarette production, the dual filter product rod may be attached to a tobacco envelope at each end (e.g. by ring tipping) prior to the final cut (in register with a position halfway along the length of the dual filter product rod to which the tobacco envelopes have been attached) to provide two recess filter cigarettes. As can be seen in Figure 5a the asymmetric cross-sections of the two elements in the dual filter product rod are mirror images of each other, so when the final cut to provide two recess filter cigarettes is made, and the cigarettes oriented in the same direction (by flipping one cigarette in the plane in which the cut was made), the asymmetric cross-sections which are visible at the ends of cigarettes are identical.

The first (longitudinally extending) element visible at the first end of the dual filter rod is preferably an extruded element and/or the second (longitudinally extending) element visible at the second end of the dual filter rod is preferably an extruded element.

The dual filter rods in the continuous flow are preferably aligned such that the longitudinally axes of their cylindrical cores are oriented along the longitudinal direction of the flow. The dual filter rods in the longitudinally advancing flow are preferably spaced longitudinally from each other (i.e. each dual filter rod is longitudinally spaced from the next along the continuous flow).

The tobacco smoke filtering material (used in aspects of the invention) may be for example any of those materials (usually filamentary, fibrous, web or extruded) conventionally employed for tobacco smoke filter manufacture. The filtering material may be natural or synthetic filamentary tow, e.g. of cotton or plastics such as polyethylene or polypropylene, or cellulose acetate filamentary tow. It may be, for example, natural or synthetic staple fibres, cotton wool, web material such as paper (usually creped) and synthetic non-wovens, and extruded material (e.g. starch, synthetic foams). It will be appreciated that the tobacco smoke filtering material used for each of the first, second and third (and forth) base rods may be the same as, or different to, the filtering material used in any other base rod.

The (e.g. extruded) element extending longitudinally of the rod may comprise a thermoplastic polymer, for example, cellulose acetate, polyethylene, polypropylene, polylactic acid, polyester or mixture thereof. Preferably, the element extending longitudinally of the rod comprises cellulose acetate. Methods of preparing cellulose acetate powder are known (e.g. see US 4228246). Cellulose ester pellets are commercially available from Rotuba Extruders of Linden, New Jersey under the trade mark "Naturacell". The cellulose ester pellets may be converted into an element. The element extending longitudinally of the rod (for example comprising an extruded thermoplastic polymer e.g. extruded cellulose acetate) may further comprise a plasticiser (e.g. triacetin). The amount of plasticiser in the element may be from 7 to 42% by weight of the element, for example from 15.1 to 35% by weight of the element. It will be appreciated that the element used for each of the first and second base rods may be the same as, or different to, the element used in the other base rod.

The first, second and third base rods according to the invention may be made as continuous rods, as is well known in the art. The continuous rod as it issues continuously from the production machine outlet is cut into finite lengths for subsequent use (i.e. combination to form dual filter rods). This cutting may be into base rods as defined and described above, or first cut into double or higher multiple (usually quadruple or sextuple) lengths for subsequent use The first, second and third base rods may be combined to form a dual filter rod by methods well known in the art.

According to the present invention in a further aspect there is provided a dual filter rod comprising a first base rod at a first end of the dual filter rod, a second base rod at a second end of the dual filter rod, and a third base rod positioned longitudinally between (and abutted to each of) the first and second base rods;

wherein the first base rod comprises a first longitudinally extending (e.g. substantially cylindrical) core of tobacco smoke filtering material; and a first element extending longitudinally of the first core (e.g. extending longitudinally through the core of tobacco smoke filtering material; extending longitudinally along the core of tobacco smoke filtering material) wherein the first element is visible at the first end of the dual filter rod; and

wherein the second base rod comprises a second longitudinally extending (e.g.

substantially cylindrical) core of tobacco smoke filtering material; and a second longitudinally extending element extending longitudinally of the second core (e.g. extending longitudinally through the core of tobacco smoke filtering material; extending longitudinally along the core of tobacco smoke filtering material), wherein the second element is visible at the second end of the dual filter rod; and

wherein the cross-section of the first element visible at the first end of the dual filter rod is a mirror image of the cross-section of the second element visible at the second end of the dual filter rod.

Preferably the dual filter rod further comprises a wrapper (engaged around the base rods), wherein a first end of the wrapper extends beyond the first end of the dual filter rod to define a first (e.g. tubular) cavity (or recess) at the first end of the dual filter rod and a second end of the wrapper extends beyond the second end of the dual filter rod to define a second (e.g. tubular) cavity (or recess) at the second end of the dual filter rod. Preferably the cross-sections of the first and second elements are asymmetric.

The dual filter rod may comprise one or more additional base rods (i.e. a fourth, fifth, sixth or greater base rod) positioned longitudinally between the first and second base rods.

According to the present invention in a further aspect there is provided a dual filter product rod comprising:

a first base rod comprising a first longitudinally extending (e.g. substantially cylindrical) core of tobacco smoke filtering material and a first element extending longitudinally of the first core of tobacco smoke filtering material (e.g. extending longitudinally through the core of tobacco smoke filtering material; extending longitudinally along the core of tobacco smoke filtering material);

a second base rod comprising a second longitudinally extending (e.g. substantially cylindrical) core of tobacco smoke filtering material and a second element extending

longitudinally of the second core of tobacco smoke filtering material (e.g. extending

longitudinally through the core of tobacco smoke filtering material; extending longitudinally along the core of tobacco smoke filtering material);

a third base rod comprising a third longitudinally extending (e.g. substantially cylindrical) core of tobacco smoke filtering material; the third base rod being abutted at one end to the first base rod;

a fourth base rod comprising a fourth longitudinally extending (e.g. substantially cylindrical) core of tobacco smoke filtering material; the fourth base rod being abutted at one end to the second base rod; and

a wrapper; wherein

the end of the first base rod which is not abutted to the third base rod (that is, the end of the first base rod which is opposite to the third base rod) is longitudinally spaced from the end of the second base rod which is not abutted to the fourth base rod (that is, the end of the second base rod which is opposite to the fourth base rod); and the wrapper is engaged around (and surrounds) the third, first, second and fourth base rods to thereby define a wrapped central cavity between the first and second base rods.

Preferably the cross-sections of the first and second elements are asymmetric. Preferably the (e.g. asymmetric) cross section of the first element (e.g. at the end of the first base rod which is not abutted to the third base rod) is the mirror image of the (e.g.

asymmetric) cross section of the second element (e.g. at the end of the second base rod which is not abutted to the forth base rod).

It will be appreciated that the dual filter product rod according to this aspect of the invention may be attached at each end to a tobacco envelope (e.g. by ring tipping) and then cut in register with a position half way along the central cavity to provide two recess filter cigarettes. The recess or cavity is formed (defined) by the portion of the wrapper which overhangs the end of the first/second base rods after the wrapper is cut.

The dual filter product rod may comprise one or more additional base rods.

In a preferred embodiment, one (or more) additional base rod(s) is located between the first and third base rods and one (or more) additional base rod(s) is located between the second and fourth base rods.

In another preferred embodiment, one (or more) additional base rod(s) is abutted to the end of the third base rod which is not abutted to the first base rod; and one (or more) additional base rod(s) is abutted to the end of the fourth base rod which is not abutted to the second base rod.

According to the present invention in a further aspect there is provided a product rod comprising a plurality (e.g. 2, 4, 6 etc.) of dual filter rods longitudinally space from each other, wherein each dual filter rod comprises a longitudinally extending core of tobacco smoke filtering material, and wherein each dual filter rod comprises a first base rod at a first end of the dual filter rod, a second base rod at a second end of the dual filter rod, a third base rod positioned longitudinally between the first and second base rods; wherein a common wrapper is engaged around (and surrounds) the plurality of dual filter rods to thereby define a wrapped cavity between adjacent dual filter rods. It will be appreciated that the common wrapper defines a wrapped cavity between each pair of adjacent dual filter rods in the product rod.

According to the present invention in a further aspect there is provided a filter or filter element comprising an longitudinally extending (e.g. substantially cylindrical) core of tobacco smoke filtering material; and an element extending longitudinally of the core (e.g. extending longitudinally through the core of tobacco smoke filtering material; extending longitudinally along the core of tobacco smoke filtering material), wherein the element is visible at least at a first end of the filter or filter element and wherein the element has an asymmetric cross-section.

Preferably the filter or filter element further comprises a wrapper (engaged around the core), wherein a first end of the wrapper extends beyond a first end of the longitudinally extending core of filtering material around which it is engaged, to define a (e.g. tubular) cavity or "recess" at the first end of the core of filtering material. The second end of the wrapper may be substantially flush with a second end of the longitudinally extending core of filtering material around which it is engaged. Preferably the (longitudinally extending) element is an extruded element. The longitudinally extending core of tobacco smoke filtering material may comprise a first core of tobacco smoke filtering material (e.g. at the first end of the filter element) which includes the element extending longitudinally of the core which is visible at the first end of the filter element; and a second core of tobacco smoke filtering material (which may not include an element extending longitudinally of the core). The second core may be located at the opposite end of the first core to the end at which the first end of the filter element is visible.

The tobacco smoke filtering material (used in filters, filter elements, dual filter product rods etc. according to aspects of the invention) may be for example any of those materials

(usually filamentary, fibrous, web or extruded) conventionally employed for tobacco smoke filter manufacture. The filtering material may be natural or synthetic filamentary tow, e.g. of cotton or plastics such as polyethylene or polypropylene, or cellulose acetate filamentary tow. It may be, for example, natural or synthetic staple fibres, cotton wool, web material such as paper (usually creped) and synthetic non-wovens, and extruded material (e.g. starch, synthetic foams).

The (e.g. extruded) element extending longitudinally of the core/rod may comprise a thermoplastic polymer, for example, cellulose acetate, polyethylene, polypropylene, polylactic acid, polyester or mixture thereof. Preferably, the element extending longitudinally of the core/rod comprises cellulose acetate. Methods of preparing cellulose acetate powder are known (e.g. see US 4228246). Cellulose ester pellets are commercially available from Rotuba Extruders of Linden, New Jersey under the trade mark "Naturacell". The cellulose ester pellets may be converted into an element. The element extending longitudinally of the core/rod (for example comprising an extruded thermoplastic polymer e.g. extruded cellulose acetate) may further comprise a plasticiser (e.g. triacetin). The amount of plasticiser in the element may be from 7 to 42% by weight of the element, for example from 15.1 to 35% by weight of the element.

According to the invention in a further aspect there is provided a method of

manufacturing a dual filter rod, or dual filter product rod, or product rod comprising a plurality (e.g. 2, 4, 6 etc.) of dual filter rods, or product comprising a plurality (e.g. 2, 4, 6 etc.) of dual filter product rods;

the method comprising the steps of:

By cutting the product rod in register with a position half way along a third base rod, and cutting the product rod in register with a position half way along the next third base rod (which is in the next dual filter rod) in the flow, a dual filter product rod will be obtained (see Fig 5a). The dual filter product rod may subsequently be cut in register with a position halfway along the length of the dual filter product rod, to provide two recess filters/filter elements for subsequent use. Often a dual filter product rod will be attached to a tobacco envelope at each end (e.g. by ring tipping) prior to the final cut (in register with a position halfway along the length of the dual filter product rod to which the tobacco envelopes have been attached) to provide two recess filter cigarettes. It will be understood that these methods are all within the aspect of the invention defined above. The third (and fourth if present) base rods according to the invention may be, for example, Combined Performance Filter (CPF) base rods (for example a base rod such as that disclosed in GB 2133269). CPF base rods feature an inner wrap that has embossed grooves over part of its length and have the advantage of providing enhanced filtration efficiency and/or lower pressure drop compared to standard cellulose acetate filters. In a less preferred embodiment, the first and second base rods may be CPF base rods in order to provide a distinctive end appearance.

The first and second base rods preferably have a length of from 5 mm to 20 mm, for example of from 7.5 to 15 mm. The third and fourth base rods according to the invention preferably have a length of from 5 mm to 40 mm, for example of from 10 to 20 mm.

A tobacco smoke filter of the invention may be of length 15 to 80 mm, e.g. 17 to 35 mm, e.g. 20 to 30 mm. The recess section of the filter tip (that is, the length by which the end of the wrapper extends beyond the end of the core around which it is engaged to define the cavity at the (e.g. mouth) end of the filter may have a length 3 to 10 mm, and is most preferably of length 4 to 6 mm. The longitudinally extending core of tobacco smoke filtering material may be of length 10 to 80 mm, e.g. 14 to 27 mm, e.g. 17 to 25 mm. The tobacco smoke filter may be of circumference 14 to 28 mm, for example 16 to 26 mm, for example 16 to 17 mm or 24 to 25 mm. The final filter cigarette may be ventilated or non-ventilated and of any circumference range traditionally used in smoking products (e.g. c. 14 to c. 28 mm circumference).

Any dual rod, dual filter product rod, filter or filter element according to the invention may contain an additive (e.g. activated carbon) and/or a flavouring agent (e.g. menthol, peppermint). The flavouring agent may be contained in one or more receptacle(s) (e.g. one or more capsule(s), e.g. one or more frangible capsule(s)). The additive and/or flavouring agent may be included in the first and/or second and/or third base rods, for example in the element that extends longitudinally of the core of tobacco smoke filtering material in the first or second base rods, or in the tobacco smoke filtering material itself. The additive and/or flavouring agent can be added by techniques known in the cigarette filter manufacturing industry, for example through direction injection. In a further example, the tobacco smoke filter may include a breakable capsule containing a flavouring agent (e.g. in the first, second, or third base rod). The additive and/or flavouring agent may modify or enhance the smoking experience. In other examples, however, the filter or filter element does not include a flavour or flavouring agent.

The wrapper may be paper, e.g. plugwrap paper, e.g. stiff plugwrap paper. The wrapper may be a porous or non porous wrapper. The wrapper may be a porous or non porous wrapper of up to 32k Cu. The wrapper may be a paper of basis weight from about 40 to about 120 g/m². The wrapper may be of basis weight from about 80 to about 120 g/m², for example a basis weight of around 100 g/m², e.g. for a recess filter of standard (c. 24-25 mm)

circumference. For slim or superslim recess filters (e.g. down to around 16-17 mm

circumference), the wrapper may be a plugwrap paper of a lower basis weight, e.g. around 50 g/m².

A cigarette comprising a filter or filter element as described herein is also envisaged within the scope of the invention.

In a filter cigarette according to the invention, a filter of the invention (or a filter which includes a filter element of the invention) [or a filter made by a method according to the invention, or a filter including a filter element made by a method according to the invention] is joined to a wrapped tobacco rod with one end of the filter towards the tobacco. The filter may, for example, be joined to the wrapped tobacco rod by ring tipping [which engages around just the adjacent ends of the (wrapped) filter and rod to leave much of the filter wrap exposed] or, more preferably, by a full tipping overwrap (which engages around the full filter length and the adjacent end of the tobacco rod). The cigarette may include a tipping overwrap (of e.g. a stiff tipping paper) in conjunction with the outer wrapper of the filter to give the desired (e.g. further increased) stiffness to the final recess filter cigarette.

Any filter or filter cigarette according to the invention may be unventilated, or may be ventilated by methods well known in the art, e.g. by use of a pre- perforated or air-permeable wrapper (plugwrap), and/or laser perforation of wrapper (plugwrap) and tipping overwrap. A ventilating full tipping overwrap may likewise be inherently air-permeable or provided with ventilation holes, and in ventilated products where both filter plugwrap and tipping overwrap are present ventilation through the overwrap will usually be in register with that through the plugwrap. Ventilation holes through a filter plugwrap, or through a tipping overwrap, or through both simultaneously, may be made by laser perforation during filter or filter cigarette production.

According to the invention in a further aspect there is provided a multiple rod comprising a plurality (e.g. 2, 4, 6 etc.) of dual filter rods as described above and/or herein joined end-to- end in a mirror image relationship.

The present invention will now be illustrated with reference to the following Examples and the attached drawings in which:

FIGURE 1 is a perspective, part cut away, view of a first base rod according to an aspect of the invention;

FIGURE 2 is a perspective, part cut away, view of a second base rod according to an aspect of the invention;

FIGURE 3 is a perspective, part cut away, view of a third base rod according to an aspect of the invention;

FIGURE 4 is a perspective, part cut away, view of a dual filter rod according to an aspect of the invention;

FIGURE 5 is a perspective, part cut away, view of a dual filter rod according to an aspect of the invention;

FIGURE 5a is a perspective, part cut away, view of a dual filter rod according to an aspect of the invention;

FIGURE 6 is a perspective, part cut away, view of a tobacco smoke filter according to an aspect of the invention;

FIGURE 7 is a perspective, part cut away, view of a product rod according to an aspect of the invention, in the continuous flow of dual filter rods;

FIGURE 8 illustrates apparatus for manufacturing the dual filter rods shown in figures 4 and 5 and the tobacco smoke filter of figure 6 according to an example of a method according to the invention.

Figure 1 is a perspective, part cut away, view of a first base rod 1 a. First base rod 1 a comprises a longitudinally extending substantially cylindrical core 2a of tobacco smoke filtering material. The substantially cylindrical core 2a is in the form of a cylindrical cellulose acetate plug of length 10 mm and circumference of around 25mm. The substantially cylindrical core 2a is made from cellulose acetate tow which has been gathered and condensed into rod form by methods which are well known in the art. First base rod 1 a also comprises a first continuous extruded element 3a, formed from extruded cellulose acetate, extending longitudinally through the substantially cylindrical core 2a, such that one end of element 3a is visible at a first end 4a of the base rod. The continuous extruded cellulose acetate element 3a is of e-shaped cross- section and extends through the body of the rod 1 a from one end to the other, thus presenting an e-shape logo visible at a first end 4a of the base rod. It will be appreciated that the e-shape is backwards at the other end of the base rod. The first base rod 1 a may be made by the method disclosed in WO201 1/058319. Methods of preparing extrusion grade cellulose acetate powder are known (e.g. see US 4228246). Extrusion-grade cellulose ester pellets are commercially available from Rotuba Extruders of Linden, New Jersey under the trade mark "Naturacell". The extrusion-grade cellulose ester pellets are converted into an extruded element, and enclosed within the base rod by, by methods well known in the art (see e.g. WO201 1/058319).

Figure 2 is a perspective, part cut away, view of a second base rod 1 b. Second base rod 1 b comprises a longitudinally extending substantially cylindrical core 2b of tobacco smoke filtering material. The substantially cylindrical core 2b is in the form of a cylindrical cellulose acetate plug of length 10 mm and circumference of around 25mm. The substantially cylindrical core 2b is made from cellulose acetate tow which has been gathered and condensed into rod form by methods which are well known in the art. Second base rod 1 b also comprises a second longitudinally extending element 3b, formed from extruded cellulose acetate, extending longitudinally through the substantially cylindrical core 2b, such that one end of element 3b is visible at a second end 4b of the base rod. The continuous extruded cellulose acetate element 3b is of e-shaped cross-section and extends through the body of the rod 1 b from one end to the other, thus presenting an e-shape logo visible at second end 4b of the base rod. It will be appreciated that the e-shape is backwards at the other end of the base rod. The first base rod 1 b may be made by the method disclosed in WO201 1/058319. Methods of preparing extrusion grade cellulose acetate powder are known (e.g. see US 4228246). Extrusion-grade cellulose ester pellets are commercially available from Rotuba Extruders of Linden, New Jersey under the trade mark "Naturacell". The extrusion-grade cellulose ester pellets are converted into an extruded element, and enclosed within the base rod by, by methods well known in the art (see e.g. WO201 1/058319). It will be appreciated that rod 1 b is effectively the same as rod 1 a, flipped by 180 degrees around a plane which is perpendicular to its longitudinal axis, halfway along its length.

Figure 3 is a perspective, part cut away, view of a third base rod 1 c. Third base rod 1 c comprises a longitudinally extending substantially cylindrical core 2c of tobacco smoke filtering material. The substantially cylindrical core 2c is in the form of a cylindrical cellulose acetate plug of length 20 mm and circumference of around 25mm. The substantially cylindrical core 2c is made from cellulose acetate tow which has been gathered and condensed into rod form by methods which are well known in the art.

Figure 4 is a perspective, part cut away, view of a dual filter rod 10, according to a further aspect of the invention. The dual filter rod includes a central third base rod 1 c (e.g. a third base rod according to Figure 3). The central third base rod 1 c is abutted at its first end 101 a to a second end 101 b of a first base rod 1 a (e.g. a base rod according to Figure 1 ). The first base rod 1 a comprises a first longitudinally extending element 3a showing an e-shape section visible at a first end 4a of the base rod 1 a. The central base rod is also abutted at its second end 101 c to a first end 101 d of a second base rod 1 b (e.g. base rod according to Figure 2). The second base rod 1 b comprises a second longitudinally extending element 3b showing ing a backwards e-shape visible at a second end 4b of the base rod 1 b.

Figure 5 is a perspective, part cut away, view of a dual filter rod 10, according to a further aspect of the invention. The dual filter rod includes a central third base rod 1 c (e.g. a third base rod according to Figure 3). The central third base rod 1 c is abutted at its first end 101 a to a second end 101 b of a first base rod 1 a (e.g. a base rod according to Figure 1 ). The first base rod 1 a comprises a first longitudinally extending element 3a visible at a first end 4a of the base rod 1 a showing an e-shape section visible at a first end 4a of the base rod 1 a (and dual filter rod 10). The central third base rod is also abutted at its second end 101 c to a first end 101 d of a second base rod 1 b (e.g. a base rod according to Figure 2). The second base rod 1 b comprises a second longitudinally extending element 3b visible at a second end 4b of the base rod 1 b showing ing a backwards e-shape visible at a second end 4b of the base rod 1 b (and dual filter rod 10). A wrapper of heavy duty plugwrap paper 13 of basis weight 100 g/m² is engaged around the dual filter rod 10. A first end 14 of the wrapper 13 extends beyond a first end 1 1 of the dual filter rod 10 and a second end 15 of the wrapper 13 extends beyond a second end 12 of the dual filter rod 10 such that a tubular cavity or "recess" is provided at both ends 1 1 , 12 of the dual filter rod 10.

Figure 5a is a perspective, part cut away, view of a dual filter product rod 1000, according to a further aspect of the invention. The dual filter rod 1000 comprises a first base rod 1 a comprising a first longitudinally extending substantially cylindrical core of tobacco smoke filtering material 2a and a first element 3a extending longitudinally through the first core of tobacco smoke filtering material 2a (as in Fig 1 ); a second base rod 1 b comprising a second longitudinally extending substantially cylindrical core of tobacco smoke filtering material 2b and a second element 3b extending longitudinally through the second core of tobacco smoke filtering material 2b (as in Fig 2); a third base rod 1 c comprising a third longitudinally extending substantially cylindrical core 2c of tobacco smoke filtering material (as in Fig 3), the third base rod 1 c being abutted at one end 101 c to the first base rod 1 a; and a fourth base rod 1 d comprising a fourth longitudinally extending substantially cylindrical core 2d of tobacco smoke filtering material, the fourth base rod 1d being abutted at one end 101 e to the second base rod 1 b. It will be appreciated that the fourth base rod is identical to the third base rod (i.e. identical to the rod of Figure 3). The dual filter product rod includes a wrapper 13 of basis weight 100 g/m². As shown in Figure 5a, the end 4a of the first base 1 a which is not abutted to the third base rod 1 c is longitudinally spaced from the end 4b of the second base rod 1 b which is not abutted to the fourth base rod 1 d. The wrapper 13 is engaged around the third 1 c, first 1 a, second 1 b and fourth 1d base rods to thereby define a wrapped central cavity 50 between the first 1 a and second 1 b base rods.

As can be seen from the Figure, the asymmetric e-shape (cross section) of the first element at end 4a (at the end of the first base rod which is not abutted to the third base rod) is the mirror image of the backwards e shape (cross section) at the end 4b of the second base rod which is not abutted to the forth base rod.

It will be appreciated that the dual filter product rod 1000 according to this aspect of the invention may be attached at each end to a tobacco envelope (e.g. by ring tipping) and then cut in register with a position half way along the central cavity 50 to provide two recess filter cigarettes. The recess or cavity is formed (defined) by the portion of the wrapper which overhangs the end of the first/second base rods after the wrapper is cut. As can be seen in Figure 5a the asymmetric cross-sections of the two elements in the dual filter product rod are mirror images of each other, so when the final cut to provide two recess filter cigarettes is made, and the cigarettes oriented in the same direction (by flipping one cigarette in the plane in which the cut was made), the e-shapes which are visible at the ends of cigarettes are identical.

Figure 6 is a perspective, part cut away, view of a tobacco smoke filter according to a further aspect of the invention. The filter comprises a longitudinally extending (e.g. substantially cylindrical) core of tobacco smoke filtering material 16 comprising a first (or second) base rod 1 a/1 b as shown in Figure 1 or Figure 2 and a third base rod 1 c (made by the methods described above). The first or second base rod 1 a/1 b comprises a longitudinally extending substantially cylindrical core 2a/2b of tobacco smoke filtering material and an element 3a/3b extending longitudinally of the core 2a/2b, visible at a first end 4a/4b of the filter 16. The element 3a/3b extending longitudinally of the core 2a/2b has an asymmetric e-shaped cross- section. The tobacco smoke filter 16 further comprises a wrapper 13 of basis weight 100 g/m² surrounding the cylindrical core such the first end 14 of the wrapper 13 extends beyond the first end 17 of the core of filtering material 2a/2b of the first 1 a or second 1 b base rod around which it is engaged, to define a tubular cavity or "recess" 18 at the first end 17 of the core of filtering material 2a/2b. The second end 15 of the wrapper 13 is substantially flush with the second end 19 of the core of filtering material 2c of the third base rod 1 c (the second end 19 of the core 16) around which it is engaged.

It will be appreciated that the asymmetric e-shape of the element 3a/3b is visible at the first end of the filter or filter element. Preferably the (longitudinally extending) element is an extruded element. It will be appreciated that the longitudinally extending core of tobacco smoke filtering material comprises a first core of tobacco smoke filtering material (e.g. at the first end of the filter element) which includes the element 3a/3b extending longitudinally of the core which is visible at the first end of the filter element; and a second core of tobacco smoke filtering material (which does not in this example include an element extending longitudinally of the core). The second core (here 1 c) may be located at the opposite end of the first core to the end at which the first end of the filter element is visible.

Figure 7 is a perspective, part cut away, view of a product rod 20. The product rod 20 comprises a plurality of dual filter rods 10 longitudinally space from each other. Each dual filter rod 10 comprises a longitudinally extending substantially cylindrical core 2 of tobacco smoke filtering material and comprises a first base rod 1 a at a first end 4a of the dual filter rod 10, a second base rod 1 b at a second end 4b of the dual filter rod 10, a third base rod 1 c positioned longitudinally between the first 1 a and second 1 b base rods. A common wrapper 13 is engaged around (and surrounds) the plurality of dual filter rods 10 to define wrapped cavities between adjacent dual filter rods in the product rod.

The product rod 20 can be produced by a method comprising the steps of:

advancing in longitudinal direction 21 a continuous flow of dual filter rods 10, wherein the dual filter rods 10 in the longitudinally advancing flow are longitudinally spaced from each other, each dual filter rod comprising a longitudinally extending substantially cylindrical core 2 of tobacco smoke filtering material; and

providing a common wrapper 13 around the continuous flow of dual filter rods 10.

The filter 16 of figure 6 may be produced by the further steps:

cutting through the product rod 20 in register with a position 22 half way along a third base rod; and

cutting through the product rod 20 in register with a position 23 half way along a space between dual filter rods 10.

Figure 8 shows an apparatus for manufacturing the dual filter rods shown in figures 4, 5 and 5a and the tobacco smoke filter of figure 6 according to the invention, which uses conventional cigarette filter making machinery.

As shown in Figure 8, a first hopper 501 releases individual pre-formed longitudinally extending substantially cylindrical first base rods 1 a, as described in figure 1 , into the continuous flow. A second hopper 502 provides individual pre-formed longitudinally extending substantially cylindrical second base rods, 1 b as described in figure 2, into the continuous flow. A third hopper 503 provides individual pre-formed substantially cylindrical third base rods 1 c, as described in figure 3, into the continuous flow. The continuous flow of base rods advances longitudinally along direction 510. The three hoppers release the base rods at the same rate as one-another. The three hoppers are arranged so that the third hopper 503 is situated between the first 501 and second 502 hoppers such that the third base rods 1 c are provided between the first 1 a and second base 1 b rods in the continuous flow.

The rods are picked up by a collator drum 520, with the collator drum "pushing" on the rods such that each first base rod 1 a in the advancing flow is arranged so that the second end 101 b of the first base rod 1 a is abutted to the first end 101 a of the third base rod 1 c, and so that the second end 101 c of the third base rod 1 c is abutted to the first end 101 d of the second base rod 1 b, to form a dual filter rod 10, such that there is a space between the first end 4a of a first base rod 1 a of any given dual filter rod 10 and the second end 4b of a second base rod 1 b of a neighbouring dual filter rod 10.

As shown in Figure 8, the longitudinally advancing flow enters a garniture 530 where it becomes entrained on a longitudinally advancing wrapper substrate in the form of a paper of basis weight 80gsm, which may be printed. The flow is arranged on a longitudinally advancing wrapper substrate 13 in the following order: first base rod 1 a + third base rod 1 c + second base rod 1 b + cavity + first base rod 1 a and so on to form a continuous wrapped product rod 20 comprising a plurality of dual filter rods 10 as shown in figure 7.

The continuous wrapped product rod 20 may then be cut (by a rotary knife or similar).

The continuous wrapped product rod 20 may be cut through in register with a position half way along a third base rod 1 c and/or the continuous wrapped product rod 20 may be cut through in register with a position half way along a space 24 between dual filter rods 10 to form a dual filter rod 10 according to Figure 5; or a dual filter product rod 1000 according to Figure 5a; or a filter 16 according to Figure 6. Thus, it will be appreciated that if it is desired to provide or a dual filter product rod 1000 according to Figure 5a, the wrapped product rod is cut through in register with a position half way along a third base rod 1 c, and cut again in register with a position half way along the next third base rod 1 c in the flow, to provide dual filter product rod 1000.

Claims

1. A method of producing a (e.g. recess) tobacco smoke filter or filter element comprising the steps of: advancing longitudinally a continuous flow of dual filter rods wherein the dual filter rods in the longitudinally advancing flow are longitudinally spaced from each other, each dual filter rod comprising a longitudinally extending core of tobacco smoke filtering material, and wherein each dual filter rod comprises; a first base rod at a first end of the dual filter rod; a second base rod at a second end of the dual filter rod; and a third base rod positioned longitudinally between the first and second base rods; providing a common wrapper around the continuous flow of dual filter rods to provide a product rod comprising a plurality of wrapped dual filter rods which are longitudinally spaced from each other within the product rod; cutting through the product rod in register with a position half way along a third base rod; and/or cutting through the product rod in register with a position half way along a space between dual filter rods.

2. A method according to claim 1 , wherein

the first base rod comprises a first longitudinally extending core of tobacco smoke filtering material; and a first element extending longitudinally of the core of tobacco smoke filtering material which is visible at the first end of the dual filter rod; and

the second base rod comprises a second longitudinally extending core of tobacco smoke filtering material; and a second element extending longitudinally of the core of tobacco smoke filtering material which is visible at the second end of the dual filter rod;

3. A method according to claim 2 wherein the cross-sections of the first and second elements are asymmetric.

4. A method according to claim 2 or claim 3 wherein the first element visible at the first end of the dual filter rod is an extruded element and/or the second element visible at the second end of the dual filter is an extruded element.

5. A method according to any preceding claim wherein the common wrapper comprises stiff plugwrap paper of basis weight 40 to 120 g/m².

6. A method of producing a tobacco smoke filter or filter element or dual filter rod or dual filter product rod or product rod comprising a plurality (e.g. 2, 4, 6 etc.) of dual filter rods or dual filter product rods substantially as hereinbefore described with reference to Figures 1 to 8.

7. A method according to any preceding claim wherein the dual filter rod comprises one or more additional base rods positioned longitudinally between the first and second base rods.

8. A dual filter rod comprising a first base rod at a first end of the dual filter rod, a second base rod at a second end of the dual filter rod, and a third base rod positioned longitudinally between the first and second base rods;

wherein the first base rod comprises a first longitudinally extending core of tobacco smoke filtering material; and a first element extending longitudinally of the first core, wherein the first element is visible at the first end of the dual filter rod; and

wherein the second base rod comprises a second longitudinally core of tobacco smoke filtering material; and a second longitudinally extending element extending longitudinally of the second core, wherein the second element is visible at the second end of the dual filter rod; and wherein the cross-section of the first element visible at the first end of the dual filter rod is a mirror image of the cross-section of the second element visible at the second end of the dual filter rod.

9. A dual filter rod according to claim 8 further comprising a wrapper, wherein a first end of the wrapper extends beyond the first end of the dual filter rod to define a first (e.g. tubular) cavity (or recess) at the first end of the dual filter rod and a second end of the wrapper extends beyond the second end of the dual filter rod to define a second (e.g. tubular) cavity (or recess) at the second end of the dual filter rod.

10. A dual filter rod according to claim 8 or claim 9 wherein the cross-sections of the first and second elements are asymmetric.

1 1. A dual filter rod according to any of claims 8 to 10 comprising one or more additional base rods positioned longitudinally between the first and second base rods.

12. A dual filter product rod comprising:

a first base rod comprising a first longitudinally extending core of tobacco smoke filtering material and a first element extending longitudinally of the first core of tobacco smoke filtering material;

a second base rod comprising a second longitudinally extending core of tobacco smoke filtering material and a second element extending longitudinally of the second core of tobacco smoke filtering material;

a third base rod comprising a third longitudinally extending core of tobacco smoke filtering material, the third base rod being abutted at one end to the first base rod;

a fourth base rod comprising a fourth longitudinally extending core of tobacco smoke filtering material; the fourth base rod being abutted at one end to the second base rod; and a wrapper; wherein

the end of the first base rod which is not abutted to the third base rod is longitudinally spaced from the end of the second base rod which is not abutted to the fourth base rod; and the wrapper is engaged around the third, first, second and fourth base rods to thereby define a wrapped central cavity between the first and second base rods.

13. A dual filter product rod according to claim 12 wherein the cross section of the first element is the mirror image of the cross section of the second element.

14. A dual filter product rod according to claim 12 or 13 wherein the cross sections of the first element and the second element are asymmetric.

15 A dual filter product rod according to any of claims 12 to 14, comprising one or more additional base rods.

16. A dual filter product rod according to claim 15 wherein one (or more) additional base rod(s) is located between the first and third base rods; and one (or more) additional base rod(s) is located between the second and fourth base rods.

17. A dual filter product rod according to claim 15 wherein one (or more) additional base rod(s) is abutted to the end of the third base rod which is not abutted to the first base rod; and one (or more) additional base rod(s) is abutted to the end of the fourth base rod which is not abutted to the second base rod.

18. A product rod comprising a plurality (e.g. 2, 4, 6 etc.) of dual filter rods longitudinally spaced from each other, wherein each dual filter rod comprises a longitudinally extending core of tobacco smoke filtering material, and

wherein each dual filter rod comprises:

a first base rod at a first end of the dual filter rod;

a second base rod at a second end of the dual filter rod;

a third base rod positioned longitudinally between the first and second base rods; and

a common wrapper engaged around the plurality of dual filter rods to thereby define a wrapped cavity between adjacent dual filter rods.

19. A filter or filter element comprising a longitudinally extending core of tobacco smoke filtering material; and an element extending longitudinally of the core, wherein the element is visible at least at a first end of the filter or filter element and wherein the element has an asymmetric cross-section.

20. A filter or filter element according to claim 19 further comprising a wrapper wherein a first end of the wrapper extends beyond a first end of the core of filtering material around which it is engaged, to define a cavity at the first end of the core of filtering material.

21. A filter or filter element according to claim 19 or claim 20 wherein the element is an extruded element.

22. A filter or filter element substantially as hereinbefore described with reference to Figure 6.

23. A filter cigarette comprising

a filter according to any of claims 19 to 22; or a filter which includes a filter element according to any of claims 19 to 22; or a filter made by a method according to any of claims 1 to 6; or a filter including a filter element made by a method according to any of claims 1 to 6 wherein the filter is joined to a wrapped tobacco rod with one end of the filter towards the tobacco.

24. A method of producing a dual filter rod or dual filter product rod or product rod comprising a plurality (e.g. 2, 4, 6 etc.) of dual filter rods or product rod comprising a plurality (e.g. 2, 4, 6 etc.) of dual filter product rods comprising the steps of: advancing longitudinally a continuous flow of dual filter rods wherein the dual filter rods in the longitudinally advancing flow are longitudinally spaced from each other, each dual filter rod comprising a longitudinally extending core of tobacco smoke filtering material, and wherein each dual filter rod comprises; a first base rod at a first end of the dual filter rod; a second base rod at a second end of the dual filter rod; and a third base rod positioned longitudinally between the first and second base rods; providing a common wrapper around the continuous flow of dual filter rods to provide a product rod comprising a plurality of wrapped dual filter rods which are longitudinally spaced from each other within the product rod; cutting through the product rod in register with a position half way along a third base rod; and/or cutting through the product rod in register with a position half way along a space between dual filter rods.