This invention relates to tobacco smoke filters having a tobacco smoke filtering core of non- circular cross section, an outer layer of air-permeable material encasing the core and, optionally, an outer wrapper engaged around the outer layer.

Concentric core cigarette filters, which comprise an inner cylindrical core of one filtering material surrounded by outer layer (annulus or annular layer) of another filtering material are known. The use of two such different filtering materials for the core and outer annular layer can give rise to an unsightly end appearance in the final filter cigarette and it is thus conventional for the concentric core filter to be employed in a dual or other multiple component filter, in addition to a plain buccal end plug of acceptable uniform end appearance. The present invention relates to "concentric" core filters in which the inner core has a defined, non-circular, cross section. This provides a distinctive and more attractive end appearance to the filter and eliminates the usual need for a concentric core filter to be combined with a plain buccal end plug, thereby reducing the cost and number of steps of the overall filter manufacturing operation. It will also be appreciated that the distinctive end appearance provided to the finished filter cigarette would be advantageous for anti- counterfeiting purposes. To provide these advantages it is necessary that the inner core is formed (with the outer layer) such that the well-defined shape is maintained in the subsequent process steps (wrapping, connection to tobacco rod, packaging the resulting cigarette etc.).

According to the present invention there is provided a method of producing a tobacco smoke filter or filter element comprising: forming a longitudinally extending outer layer (e.g. a substantially annular outer layer) of tobacco smoke filtering material around a continuously advancing longitudinally extending (inner) core of tobacco smoke filtering material of non- circular cross section.

The longitudinally extending outer layer may be formed around the continuously advancing (inner) core of non-circular cross section by continuously advancing the longitudinally extending (inner) core through a hollow tube; continually advancing a flow of tobacco smoke filtering material along (e.g. along and around) the outer surface of the hollow tube; and condensing (e.g. drawing and gathering e.g. by means of a garniture) the continually advancing tobacco smoke filtering material (from the flow) around the continuously advancing (inner) core as the core exits the hollow tube. The condensed filtering material forms the outer layer (of tobacco smoke filtering material). Preferably the filtering material which forms the outer layer is a cellulose acetate tow, optionally including a plasticiser (e.g. glyceryl triacetate). The method may include a further step of heat treating the advancing outer layer of tobacco smoke filtering material as and/or or shortly after it is formed (e.g. condensed) around the continuously advancing longitudinally extending (inner) core of tobacco smoke filtering material of non-circular cross section, optionally with a subsequent cooling step. The heat treatment (and optional cooling) may activate the plasticiser to form the filtering material into a coherent, bonded, smoke- permeable structure around the shaped core.

The continuously advancing longitudinally extending (inner) core of tobacco smoke filtering material of non-circular cross section may be formed immediately or substantially immediately prior to forming the longitudinally extending outer layer of tobacco smoke filtering material around the core, for example as part of the same continuous in-line process. The continuously advancing longitudinally extending (inner) core of tobacco smoke filtering material of non-circular cross section may be formed by continuously advancing (e.g. continuously drawing and/or gathering) a flow of tobacco smoke filtering material through a shaped die of non-circular cross section. Preferably the filtering material which forms the longitudinally extending (inner) core is a cellulose acetate tow, optionally including a plasticiser (e.g. glyceryl triacetate). The method may include a further step of heat treating the advancing longitudinally extending (inner) core as and/or or shortly after it is formed [e.g. as and/or or shortly after it is formed by continuously advancing (e.g. continuously drawing and/or gathering) a flow of tobacco smoke filtering material through a shaped die of non- circular cross section], optionally with a subsequent cooling step. The heat treatment (and optional cooling) may activate the plasticiser to form the filtering material into a coherent, bonded, smoke-permeable shaped longitudinally extending (inner) core.

The defined method of manufacture overcomes the prob)ems of forming a shaped core and maintaining a well-defined shape for the core because the pre-formed core is drawn and combined with the outer material in a second step (e.g. in a second garniture).

The method may provide filters and filter elements having distinctive and attractive end appearance, thereby eliminating the usual need for a concentric core filter to be combined with a plain buccal end plug, and reducing the cost and number of steps of the overall filter manufacturing operation. The distinctive end appearance provided to the finished filter cigarette may be advantageous for anti-counterfeiting purposes.

Thus, according to the present invention there is provided a tobacco smoke filter or filter element (e.g. formed by the method according to the invention) comprising a longitudinally extending inner core of tobacco smoke filtering material; and a longitudinally extending outer layer of tobacco smoke filtering material engaged around the longitudinally extending inner core; wherein the longitudinally extending inner core is of non-circular cross section. Preferably the longitudinally extending outer layer of tobacco smoke filtering material is engaged around (e.g. surrounds) the longitudinally extending inner core such that the outer face of the inner core is enclosed by the longitudinally extending outer layer of tobacco smoke filtering material. The filter or filter element is generally circular or oval in cross section. The longitudinally extending inner core may be of star shaped, triloba), pentagonal, cog-shaped, heart-shaped or logo shaped cross section, or other non-circular cross section. Preferably, the longitudinally extending core of tobacco smoke filtering material of non- circular cross section does not have a helical cross section. The inner core and/or outer core may comprise a cellulose acetate tow, optionally including a plasticiser. The inner core and/or outer core may include a pigment. The inner core is preferably of a contrasting colour to the outer layer. The tobacco smoke filter or filter element may include an extending wrapper arranged around the tobacco smoke filter or filter element. The outer layer preferably adheres to the core material to resist separation.

The choice of the inner core and outer layer (surrounding substantially annular body) and the ventilation (if any) employed in the final cigarette filter enables the smoke stream to be predominantly channelled through one component (inner core, outer layer) of the filter, for example to take advantage of the filtration characteristics provided by that particular filter component. This can be achieved through selection of appropriate levels of pressure drop and retention level provided by the inner core and outer layer, together with the ventilation level of the finished cigarette, to direct the smoke flow path through the inner core or outer layer. The present invention can thereby provide enhanced filtration characteristics combined with visual differentiation characteristics provided by the end appearance. For example, when used in a ventilated cigarette, the filter can give a significant reduction of carbon monoxide and vapour phase compounds found in smoke without reducing tar levels by the same extent as a ventilated cigarette employing a conventional filter. This enables the cigarette taste and acceptable pressure drops to be maintained, especially in ultra low-tar cigarettes, whilst reducing the levels of carbon monoxide and other volatile smoke compounds.

Preferably, the (inner) core and the outer layer (surrounding substantially annular body) are of gathered and bonded cellulose acetate tow. Other fibrous or filamentary material may also be employed in either the core or the outer layer. Preferably, the (inner) core will (include pigment and) be of a different colour to the outer layer to accentuate the end appearance of the filter. For example, the shaped core may be red, blue, green or black in colour and the outer layer may be white. When a coloured (pigmented) material is used in the inner core and the filter or filter ventilation components (outer layer, wrapper) are selected so as to channel smoke predominantly along the core, a reduced impression of staining is advantageously obtained after the cigarette has been smoked. Alternatively, if a white core and a white outer layer are both used, it is possible for the shape of the core to become more apparent during smoking due to enhanced staining of the core resulting from smoke being channelled along the core. Such a feature may serve as an anti-counterfeit feature and/or to enhance brand identity.

According to the present invention in a further aspect there is provided a method of producing a tobacco smoke filter or filter element comprising a step of aligning side-by-side two or more longitudinally extending portions of tobacco smoke filtering material each having a uniform cross section to form a longitudinally extending cylindrical core of tobacco smoke filtering material having a uniform solid cross section. Herein the phrase "solid cross section" means that the cylindrical core has a circular (or oval) cross section (formed by the combination of longitudinally extending portions of tobacco smoke filtering material) which does not have (longitudinally extending) gaps or spaces between the portions. In other words the cylindrical core of tobacco smoke filtering material having a uniform solid cross section presents a fully circular or oval (gap free) face at its end. The "solid cross section" is air permeable.

Thus, according to the present invention in a still further aspect there is provided a tobacco smoke filter or filter element (e.g. formed by the method according to the invention) including a plurality of longitudinally extending portions of tobacco smoke filtering material each having a uniform cross section; the plurality of longitudinally extending portions being aligned side- by-side to form a longitudinally extending cylindrical core of tobacco smoke filtering material having a uniform solid cross section. The tobacco smoke filter or filter element may include two longitudinally extending portions of tobacco smoke filtering material each having a uniform cross section; the longitudinally extending portions being aligned side-by-side to form a longitudinally extending cylindrical core of tobacco smoke filtering material having a uniform solid cross section. The boundary between adjacent longitudinally extending portions which are aligned side-by-side may be of elongated S shape in cross section. Two or more of the longitudinally extending portions of filtering material may be of contrasting colours. The tobacco smoke filter or filter element may further comprise an extending wrapper arranged around the tobacco smoke filtering or filter element. In this aspect of the invention the two (or more) filter materials are aligned in a side-by-side alignment rather than in a coaxial arrangement. These two side-by-side components may be of different colours and the boundary between the tow components can follow a defined shape, e.g. an elongated 'S' , so the end of the filter or filter element presents a circular face looking like a stylised Ying Yang symbol (e.g. as shown in Fig 3).

A filter or filter element according to any aspect of the invention is preferably wrapped in an outer plug wrap. This plug wrap may be porous or non-porous. The filters according to the invention are preferably formed in a continuous length and then cut into finite lengths. These may be a multiple (e.g. quadruple or sextuple) of the length of the eventual filter tips. The filter tips may be of circumference between 14 and 28 mm and of length between 15 and 40 mm.

The tobacco smoke filter or filter element according to the invention 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. A tobacco smoke filter of the invention may be of length 10 to 40 mm, e.g. 15 to 35 mm, e.g. 20 to 30 mm. A tobacco smoke filter element of the invention may be of length 5 to 30mm, e.g. 6 to 20mm, e.g. 8 to 15 mm, e.g. 10 to 12 mm.

Filters and filter elements according to the invention may be used in machine made cigarettes (e.g. those mass produced and packaged). Filters and filter elements according to the invention may also be used as (or in) a filter tip for use with a individually rolled cigarette (e.g a hand rolled cigarette) or a Roll Your Own or Make-your-own product.

A filter element according to the invention may also be used as the mouth-end segment of a multi-segment filter, e.g. a dual, triple, other multiple filter. Such filters are well known in the art.

The invention includes any filter cigarette made using a filter according to the invention.

Detailed description of the invention

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

FIGURE 1 shows an end of an example of a filter according to the invention;

FIGURE 2 shows an end of a second example of a filter according to the invention;

FIGURE 3 shows an end of a third example of a filter according to the invention; and

FIGURE 4 is a schematic side elevation view of an apparatus for forming filters according to the invention by the method of the invention. Filters and filter elements of the invention may be conveniently made by using crimped continuous filaments of cellulose acetate and bonding them to each other. Other fibrous or filamentary materials may also be employed. The core and outer layer materials each preferably comprise continuously crimped filamentary tows of cellulose acetate and these two filamentary tow streams are treated separately prior to being combined within the second garniture of a filter making machine.

In FIGURE 4, a first stream of cellulose acetate tow (11) (which will form the inner core) is continuously drawn from one or more bales (not shown) and treated by longitudinally stressing each filamentary tow to separate the filaments, forming the filaments into a thinly spread layer, and spraying the tow with glycerol triacetate plasticiser. The stream of tow is drawn over a guide (12) into two sets of rollers (13, 13a and 14, 14a). Rollers (14, 14a) rotate faster than rollers (13, 13a) causing the tow to be stretched and opened to form a web of first filter material of width of approximately 250 mm. The web of tow then passes into a spray booth (15) where it is sprayed with glycerol triacetate before exiting the spray booth via a set of delivery rollers (16, 16a). These are methods well known in the art. The continuously advancing treated tow (11) is gathered and drawn, by means of a garniture (13) and an endless tape, through a shaped die (14). In this die, steam is passed in a radial direction directly into contact with the tow filaments, so that they are rapidly heated and, by the solvent action of the glycerol triacetate, caused to adhere to each other to form an inner core (11a) of tobacco smoke filtering material of the desired cross section (e.g. a star as shown in Fig 1). The die (14), and resulting inner core (11a), may be of any desired shape, for example star, triangle, pentagon or heart-shaped.

A second longitudinally advancing stream of cellulose acetate tow (21) is used to form the outer layer. Again, the tow is continuously drawn from one or more bales and treated by longitudinally stressing each filamentary tow to separate the filaments, forming the filaments into a thinly spread layer, and spraying the tow with glycerol triacetate plasticiser, by methods well known in the art (not shown in Fig 4). Once treated, the second stream is applied around the inner core, as follows.

The continually advancing inner core of tobacco smoke filtering material of the desired cross section (11a) is advanced into and through a hollow tube (15) within an enclosure (16). The longitudinally advancing second stream of filamentary tow (21) is passed, by means of a further garniture and endless tape, around the hollow tube, such that it is advancing in the same direction as the inner core (in the direction of arrow 23). The second stream of tow (21) condenses around the shaped inner core as the core advances and exits the hollow tube, thereby forming a substantially annular outer layer of filtering material (21a) around the inner core (1 1 a). The hollow tube (15) is located in the enclosure such that the inner core becomes centrally located within the finished filter. Steam is passed through the endless tape into contact with the enveloping filaments of the second stream of tow during their passage through the enclosure so as to activate the glycerol triacetate bonding constituent contained thereon, whereupon they form a coherent, bonded, smoke-permeable (outer) layer around the shaped core. The resulting continuously advancing filter rod (31 ) formed by condensing the outer layer around the continuously advancing longitudinally extending (inner) core of non-circular cross section is advantageously cooled immediately after formation. A wrapper is provided in the conventional manner, i.e. by means of the usual wrapping garniture which will be disposed immediately upstream of the cutter. Thus, the process provides a filter rod (31 ) comprising a longitudinally extending inner core (1 1 a) of tobacco smoke filtering material; and a longitudinally extending outer layer (21 a) of tobacco smoke filtering material engaged around the longitudinally extending inner core; wherein the longitudinally extending inner core is of non-circular cross section. The filter rod may be cut into single or multiple filter or filter element lengths for subsequent use (ie. as filters or filter elements, or for combination with other filters or filter elements), by methods known in the art.

Thus, the filamentary material for the longitudinally extending core component is passed into a die and garniture arrangement to form the desired (non-circular) shape and the so-formed core is subsequently surrounded and encompassed by the filamentary material of the outer layer as it passes through a further garniture to provide a continuous filter rod. The method of manufacture described above overcomes the problems of forming a shaped core and maintaining a well-defined shape for the core because the core is drawn and combined with the annular material in the second garniture after the core is formed.

Figure 1 shows one end of a filter (or element or rod) according to the invention, made by the process above. The filter comprises an inner core of plasticised cellulose acetate filamentary tow having a cross section in the shape of a five-pointed star (1 ) intimately surrounded by an outer layer of plasticised white-coloured cellulose acetate filamentary tow (2) encased in a plugwrap paper (3).The cellulose acetate tow which forms the core includes a green pigment which contrasts with the white of the outer layer, and provides a distinctive end appearance. It will be appreciated that a star shaped die is used to form the core.

Figure 2 shows one end of another filter (or element or rod) according to the invention, made by the process above. The filter comprises a core of red-coloured (pigmented) plasticised cellulose acetate filamentary tow in the shape of heart (1 a) intimately surrounded by an annulus of white-coloured plasticised cellulose acetate filamentary tow (2b) encased in a plugwrap paper (3). It will be appreciated that a heart shaped die is used to form the core, and the contrast between the red heart-shaped core and white surrounding layer provides a distinctive end appearance.

In a further embodiment, it is possible to use a similar process to manufacture a filter or filter element by aligning side-by-side (rather than in a coaxial arrangement) two or more longitudinally extending portions of tobacco smoke filtering material each having a uniform cross section and drawing and gathering them through a garniture to form a longitudinally extending cylindrical core of tobacco smoke filtering material having a uniform solid cross section. Thee two side-by-side portions may be of different colours and the boundary between the tow components can follow a defined shape, e.g an elongated 'S' or stylized Ying Yang symbol.

Figure 3 shows one end of another filter (or element or rod) according to the invention, made by the adapted process described above. Two different coloured plasticised filamentary tows of cellulose acetate are arranged side-by-side. The filter comprises a green-coloured filter material (1 b) and a black-coloured filter material (2b) that form two distinct regions, with the boundary between them following an 'S' shaped curve. The filter is encased in a plugwrap paper (3b). The contrasting green and black layers provide a distinctive end appearance.