Patent Description:
Cigarettes and other smoking articles contain a charge of tobacco which may be combusted to produce smoke which is inhaled by a user. Filters for smoking articles are used to modify the smoke resulting from the combustion of tobacco before it reaches the user's mouth. Filters known in the art for this purpose may b formed from a plug of fibrous cellulose acetate or other materials with similar physical properties. Cellulose acetate is known to absorb particulate smoke constituents in particular. To enhance the removal of certain smoke constituents various additives may be added to smoking article filters. Examples include smoke adsorbents such as activated carbon which adsorbs certain smoke constituents thus removing them from the smoke stream passing through the filter. In addition to removing constituents from smoke, filter additives may impart characteristics to smoke passing through the filter. For example, fragrances and flavourants may be incorporated which alter the aroma and taste characteristics of smoke that has passed through the filter. Traditionally, smoking articles with filters incorporating the features described above are sold together in packs, with the smoking articles in each pack sharing the same flavours, fragrances and sorbent characteristics. As such, a user cannot customise his smoking articles to deliver a smoke profile to his choosing.

It is known from <CIT> to provide an insertable filter unit for a smoking article, the insertable filter unit comprising a retaining means to retain the insertable filter unit in a recess in the smoking article filter. The insertable filter unit has a thin insertable part and a thicker non-insertable part.

Embodiments of the invention described in more detail hereinafter provide an insertable filter unit for a smoking article filter, the insertable filter unit comprising a retaining means to retain the insertable filter unit in a recess in the smoking article filter, the insertable filter unit having a thin insertable part arranged to be inserted into the recess and a thicker non-insertable part, and wherein the insertable filter unit comprises a smoke modifying substance comprising a flavourant comprising tobacco, and filtration material.

According to another aspect of the invention, there is provided a smoking article comprising a smoking article filter comprising a recess, and an insertable filter unit comprising a retaining means to retain the insertable filter unit in said recess, the insertable filter unit comprising a thin insertable part arranged to be inserted into the recess and a thicker non-insertable part, and wherein the insertable filter unit comprises a smoke modifying substance comprising a flavourant comprising tobacco and filtration material.

The smoking article may comprise a cigarette, such as a combustible cigarette.

The above advantages and features are of representative embodiments, presented to assist in understanding the invention, and are not exhaustive and/ or exclusive. It should be understood that they are not to be considered limitations on the invention as defined by the claims, or limitations on equivalents to the claims. Additional features and advantages of the invention will become apparent in the following description, from the drawings, and from the claims.

So that the present invention may be readily understood embodiments thereof will now be described for illustrative purposes only with reference to <FIG> of the accompanying drawings, in which:.

<FIG> and <FIG> and their related description are provided by way of background information only and do not form embodiments of the invention, which is described with reference to <FIG>.

<FIG> shows a smoking article <NUM> having a buccal end <NUM> and a distal end <NUM>. The smoking article <NUM> comprises a tobacco rod <NUM> and a filter <NUM> attached thereto. The tobacco rod <NUM> is wrapped in tobacco wrapping paper <NUM>.

The filter <NUM> is shown in more detail in <FIG>. The filter <NUM> comprises a cylindrical filtration region <NUM> and a tubular filtration region <NUM> downstream of the cylindrical filtration region <NUM>. The cylindrical filtration region and the tubular filtration region <NUM> may be formed from filtration material such as fibrous cellulose acetate or other material known in the art.

The cylindrical filtration region <NUM> may be about <NUM> in length and the tubular filtration region <NUM> may be about <NUM> in length.

The filtration material of the cylindrical filtration region <NUM> may be impregnated with adsorbent material such as activated carbon which may be in bead, granule or thread form. An example of the filter <NUM> containing an activated carbon section is shown in <FIG>. In this example the cylindrical section <NUM> is a dual filter section comprising a region of filtration material 21A such as cellulose acetate and an upstream region 21B comprising activated carbon. The region of filtration material 21A may be about <NUM> in length and the region 21B comprising activated carbon may be about <NUM> in length. Alternatively, the cylindrical section <NUM> may be provided as a triple filter section, comprising two regions of filtration material without activated carbon on either side of a central region comprising activated carbon. The cylindrical region <NUM> and the tubular filtration region <NUM> may be wrapped in a plugwrap <NUM>. The filter <NUM> may be attached to the tobacco rod <NUM> using tipping paper <NUM> which circumscribes the filter <NUM>. The tipping paper <NUM> shown in <FIG> is slightly longer than the filter <NUM> so that an overlap is formed when the tipping paper <NUM> is wrapped around the filter <NUM>. This overlap may have some form of adhesive, such as glue, applied to the inner surface thereof which, in use, adheres to the outer surface of the tobacco wrapping paper <NUM>. Other attachment means for attaching the filter <NUM> to the tobacco rod <NUM> that are known in the art may also be employed.

In certain examples, the plugwrap <NUM> may be provided with carbon granules adhered to an inside surface of said plugwrap <NUM> in patches using a suitable adhesive.

The filter <NUM> has a recess <NUM>, defined by the cylindrical filtration region <NUM> and the tubular filtration region <NUM>, the recess <NUM> extending from the buccal end <NUM> arranged to accommodate a cylindrical filter insert unit <NUM>. The recess <NUM> extends at least along part of the length of the filter <NUM>. The shape of the recess <NUM> may be designed to match the shape of the filter insert unit <NUM>. In the examples shown in <FIG>, the cylindrical filter insert unit <NUM> matches the hollow cylindrical shape of the recess <NUM>.

<FIG> shows an alternative filter <NUM>. In this example the tipping paper <NUM> which wraps the cylindrical filtration material <NUM> is formed from a rigid card-like material which extends beyond the buccal end of the cylindrical filtration material <NUM> to form a recess <NUM> into which filter insert units <NUM> may be inserted. In this example, no tubular filtration region <NUM> is employed. An alternative to the filter <NUM> shown in <FIG> is a configuration similar to that shown in <FIG> except that the tubular filtration region <NUM> is replaced with a cardboard tube. In this embodiment the tipping paper <NUM> would be formed from conventional tipping paper material that is less rigid than the card-like material described above with reference to <FIG>. In this alternative example, the plugwrap <NUM> may be shorter than that shown in <FIG>, circumscribing only the cylindrical filtration material <NUM>. The filter insert unit <NUM> may have varying dimensions, such as length and diameter, and may be used in conjunction with smoking articles of varying dimensions.

Filters <NUM> and filter insert units <NUM> may be used in conjunction with varieties of smoking articles with dimensions ranging from 'demislim' to 'king size'- terms which are well known in the art. Preferably, the filter insert unit has a length between about <NUM> and about <NUM>.

The filter insert unit <NUM> may be formed from filtration material such as cellulose acetate or other smoking article filtration material known in the art and may be wrapped circumferentially with a plugwrap or other suitable material. The wrapper may be embossed with raised areas being about <NUM> in size according to one example. The material may act as a particulate absorbent of smoke constituents. In one eexample, the filter insert unit <NUM> comprises non-wrapped acetate fibres bound together using a level of plasticiser higher than levels of plasticiser used in examples where the filter insert unit <NUM> is wrapped.

In another example, the filter insert unit <NUM> may comprise randomly oriented discrete short length cellulose acetate fibres and may be manufactured using a manufacturing apparatus such as the Turmalin apparatus available from Hauni Maschinenbau AG in Germany.

The filter insert unit <NUM> may comprise reconstituted tobacco paper or compressed cut tobacco leaf which may be wrapped in reconstituted paper or a plugwrap of a type known in the art. The filter insert unit <NUM> may contain one or more flavourants in liquid form or in other forms such as granules, particles or the like.

Tobacco rods, formed in a conventional manner, may be cut to dimensions suitable for use as a filter insert unit <NUM> and may be wrapped using a suitable wrapper such as cigarette paper or a plugwrap. The wrapper may be embossed with individual raised areas being less than about <NUM> in size. If the filter insert unit <NUM> has embossed wrappers, the full length of the filter insert unit <NUM> may be embossed or only a partial length of the filter insert unit <NUM> may be embossed. The filter insert unit <NUM> may be embossed in a banded pattern.

The filter insert unit <NUM> may be arranged to achieve an effect which is known in the art as the Dalmatian effect. The Dalmatian effect may be achieved using carbon granules, tobacco in whole leaf form, reconstituted tobacco or other botanicals or their derivatives, such as menthol, added to filter tow, such as cellulose acetate tow, to produce a mottled effect.

The filter insert unit <NUM> may comprise a combination of a filtration material such as cellulose acetate with reconstituted tobacco paper and/or compressed cut tobacco leaf and/ or materials used to obtain a visual Dalmatian effect and/ or a thread. In this case, the filter insert unit <NUM> may be wrapped in reconstituted tobacco paper or a plugwrap of a type known in the art.

The filter insert unit <NUM> comprises flavourant comprising tobacco. In addition to tobacco it may comprise flavourants such as, for example only, menthol, lemon, orange, lime, coffee or tea. Menthol, tea and so forth, may be added to the filter insert unit <NUM> in whole leaf form and/ or as extracts.

In some embodiments, the filter insert unit <NUM> may comprise cut laminar tobacco and/ or one or more additives selected from mint, borage, tea, various herbs or any other suitable additive.

The filter insert unit <NUM>, when inserted, is arranged to modify characteristics of smoke as the smoking article <NUM> is smoked by a user. It should be understood that the smoking article <NUM> may equally be smoked with no filter insert unit <NUM> inserted in the recess <NUM>. The materials of the cylindrical filtration region <NUM>, tubular filtration region <NUM> may be such as to provide a pressure drop that corresponds to the pressure drop of a conventional smoking article when a user draws on the buccal end <NUM> of the smoking article <NUM>. The filter insert unit <NUM> may be arranged not to alter the pressure drop significantly when inserted into the recess <NUM> of the filter <NUM>. The filter <NUM> may contain flavourants such as menthol and so forth. Filter insert units <NUM> intended for insertion into mentholated or otherwise flavoured smoking articles may contain additives arranged to complement the smoking experience of the smoking article. The filter insert unit <NUM> may contain water. Preferred water-containing filter insert units <NUM> comprise capsules such as the capsule <NUM> described below with reference to <FIG> with the water stored inside the capsule <NUM>.

Adsorbents such as activated carbon granules, capsules or threads may also be incorporated into the filter insert unit <NUM>.

The filter insert unit <NUM> may comprise activated carbon granules packed together using a binder or the filter insert unit <NUM> may comprise carbon having a monolithic structure. Monolithic carbon structures, or carbon monoliths, are units of carbon which are not granular, but, in common with granular activated carbon, have a large surface area. Carbon monoliths do not require the use of a binder, so that the surface area of the carbon that can be used to adsorb target smoke constituents may be increased with respect to carbon structures that use a binder. Suitable monolithic carbon structures can be formed by extrusion and an example of a suitable monolithic structure and method of producing the same is described in <CIT>.

Colourants may also be incorporated and may provide a visual cue to a user, for example to provide an indication of the contents of the filter insert unit <NUM> such as flavourants or adsorbents. For example, a green colourant may be used to indicate that the filter insert unit <NUM> is mentholated.

If a filter insert unit <NUM> is to be inserted into the filter <NUM> of a smoking article <NUM> it may be useful to provide additional means for securing the filter insert unit therein. <FIG> illustrate a variety of examples of filters <NUM>, filter insert units <NUM> and the way in which they are retained in the filter <NUM>. In the description below it should be understood that retaining means indicates structure that retains beyond what may be achieved by ordinary frictional contact between two substantially flat surfaces in contact.

For illustrative reasons only, tobacco rods such as the tobacco rod <NUM> shown in <FIG> have been omitted from the following figures. It is intended that the examples listed hereinafter are consistent with those set out above with any additional modifications that may be necessary being evident to those skilled in the art.

<FIG> shows a filter <NUM> and filter insert unit <NUM> substantially similar to that described above with reference to <FIG> and <FIG>. However, this example differs from that described above in that the tubular filtration region <NUM> is shorter in length than the tubular filtration region <NUM> shown in <FIG>. A gap <NUM> is provided between the tubular filtration region <NUM> and the cylindrical filtration region <NUM>. The filter insert unit <NUM> may be formed from a compressible material which, once inserted into the recess <NUM>, expands at least partially into the gap <NUM>. The filter insert unit <NUM> may thus be secured in the recess <NUM>.

<FIG> shows an arrangement of a filter insert unit <NUM> and filter <NUM> comprising a recess <NUM>. The filter insert unit <NUM> has a number of small hooks <NUM> arranged on the major surface thereof and the inner surface of the recess <NUM> may have a corresponding number of small loops (not shown) arranged thereon to engage with the hooks <NUM> when the filter insert unit <NUM> is inserted. For example, the filter insert unit <NUM> and/ or the interior of the recess <NUM> may be provided with Velcro (RTM). As such, once the filter insert unit <NUM> has been inserted into the recess <NUM>, the resistance to removing the filter insert unit <NUM> is enhanced so that accidentally removing the filter insert unit <NUM> is more difficult.

<FIG> shows a filter <NUM> and a filter insert unit <NUM> with an alternative mechanical locking means. The filter insert <NUM> has a raised locking part <NUM> situated on the outer surface and at one end of the filter insert unit <NUM>. A corresponding depression <NUM>, of complementary shape to the raised locking part <NUM>, is situated in the recess <NUM> and may be located away from the buccal end <NUM> of the filter <NUM>. Upon insertion, the filter insert unit <NUM> may be rotated to align the raised locking part <NUM> with the depression <NUM> in the recess <NUM> to secure the filter insert unit <NUM> in the recess <NUM> of the filter <NUM>.

<FIG> shows a filter <NUM> and a filter insert unit <NUM> with yet another alternative mechanical locking mechanism. The surface of the filter insert unit <NUM> is provided with several raised spots <NUM> arranged thereon to improve the frictional fit between the recess <NUM> of the filter <NUM> and the filter insert unit <NUM>. The raised areas may be formed by outwardly perforating an outer wrapper of the filter insert unit <NUM>.

Securing the filter insert unit <NUM> inside the recess <NUM> of the filter <NUM> may alternatively be achieved by forming the filter <NUM> and the filter insert unit <NUM> from materials of differing compressibility.

<FIG> shows a filter <NUM> with a recess <NUM> located therein and a filter insert unit <NUM>. In this example, the filter insert unit <NUM> is formed from a material that is softer than the material used to form the filter <NUM>. In this embodiment, the diameter Dl of the filter insert unit <NUM> is greater than the diameter D2 of the recess <NUM>. In use, the filter insert unit <NUM> may be compressed by a user to ease insertion. Once inserted, the outward pressure on the inner walls of the recess <NUM>, exerted by the filter insert unit <NUM> returning towards its original, uncompressed dimensions serves to hold the filter insert unit <NUM> securely in place.

<FIG> shows an alternative example which also relies on the compressibility of the filter insert unit material. An inwardly extending lip <NUM> is situated at the buccal end <NUM> of the filter <NUM>. The diameter D3 of the recess <NUM> at the buccal end <NUM> where the lip <NUM> is located is smaller than the diameter D2 (shown in <FIG>) of the remainder of the recess <NUM> as well as the diameter of the filter insert unit <NUM>. Upon insertion, the filter insert unit <NUM> may be compressed to a smaller diameter so that it may be pushed past the lip <NUM> and into the recess <NUM>. The filter insert unit <NUM> may then expand substantially back to its natural, uncompressed diameter and a secure fit between the filter insert unit <NUM> and the filter <NUM> may be obtained.

<FIG> shows an alternative filter <NUM> where the tubular filter region <NUM> comprises an upstream portion 22A and a downstream portion 22B. The two portions 22A and 22B may have the same diameter or different diameters. In one example, the downstream portion 22B may be of a smaller diameter than the upstream portion in which case the downstream portion 22B may act as a lip in a similar fashion to the lip <NUM> described above with reference to <FIG>. In this example the filter insert unit <NUM> may be formed from a manually compressible material.

<FIG> shows a filter <NUM> with an end cap <NUM> attached to the buccal end <NUM> thereof. The filter insert unit <NUM> is inserted and the end cap <NUM> may then be closed. The end cap <NUM> shown in <FIG> is hinged about a point <NUM> on the buccal end <NUM> of the filter <NUM> however other means for securing the end cap <NUM> to the filter <NUM> apparent to those skilled in the art may be used instead. The end cap <NUM> is formed from a material that is substantially permeable to smoke. The filter insert unit <NUM> may be dimensioned to allow the end cap <NUM> to be closed without compression.

Alternatively, the end cap <NUM> may squeeze the filter insert unit <NUM> if the filter insert unit <NUM> is formed from a compressible material.

A gate <NUM> may be attached to the buccal end <NUM> of the filter <NUM> about a pivot <NUM>, as shown in <FIG>. The gate <NUM> and pivot <NUM> may be arranged so that the gate <NUM> opens inwardly (as shown by the curved arrow) but not outwardly. In use, the filter insert unit <NUM> is pushed into the recess <NUM> of the filter <NUM> and in so doing the gate <NUM> is pushed inwardly such that it is substantially parallel to the longitudinal axis X of the filter <NUM> as shown in <FIG>. If the filter insert unit <NUM> is manufactured from a manually compressible material pressure may then be applied to compress the filter unit <NUM> so that the end nearest the buccal end <NUM> of the filter <NUM> is pushed past the gate <NUM>. The gate <NUM> may be biased so that it returns to a position substantially perpendicular to the longitudinal axis X when the gate <NUM> is unobstructed.

<FIG> shows an alternative filter <NUM> with a recess <NUM> located therein and the filter insert unit <NUM>. In side-on cross-section, as shown in <FIG>, the recess <NUM> and filter insert unit <NUM> appear trapezoidal. A filter insert unit <NUM> formed from a manually compressible material and which is rectangular in cross- section may also be inserted into a cross-sectionally trapezoidal recess <NUM> to obtain a secure fit.

<FIG> shows an alternative filter <NUM> with a recess <NUM> located therein and a filter insert unit <NUM> with compressible flutes <NUM> located thereon. The flutes <NUM> are formed from a plurality of ridges radially disposed about the filter insert unit <NUM> and extending substantially parallel to the axis and along part of the length of the filter insert unit <NUM>. The parts of the filter insert unit <NUM> not covered by the flutes <NUM> form bar sections <NUM>. In use, the bar sections <NUM> provide means for gripping the filter insert unit <NUM> and locating the filter insert unit <NUM> in the recess <NUM> of the filter <NUM>. Before insertion, the flutes <NUM> are biased so as to protrude outwards from the rest of the filter insert unit <NUM>. Once the filter insert unit <NUM> has been fully inserted into the recess <NUM> the flutes <NUM> are compressed thus ensuring a secure fit.

An alternative to providing mechanical locking mechanism is to provide a chemical locking mechanism such as that shown in <FIG>. The outer surface of the filter insert unit <NUM> is coated with an adhesive A and the inner surface of the recess <NUM> coated with an adhesive B. In use, as the filter insert unit <NUM> is inserted into the recess <NUM> adhesive A comes into contact with the adhesive B and a chemical reaction leads to a bond being formed between the filter <NUM> and the filter insert unit <NUM>. Alternatively, the filter insert unit <NUM> may contain a frangible capsule <NUM>, as shown in <FIG>. Once the filter insert unit <NUM> has been inserted into the recess <NUM>, the filter <NUM> is squeezed inwardly in the direction of the mutually facing arrows shown in <FIG>. The frangible capsule <NUM> is ruptured and adhesive stored therein is released. The insert unit <NUM> may be formed from a material that allows migration of the adhesive to the outer surface of the insert unit <NUM>. The adhesive bonds the filter <NUM> and the filter insert unit <NUM> together.

The frangible capsule <NUM> may contain water as well as, or instead of, adhesive together with any flavourant, colourant or sorbent described herein.

An alternative arrangement of adhesive between the filter <NUM> and the filter insert unit <NUM> is shown in <FIG>. In this example adhesive is applied to the outer surface of the insert unit <NUM> only. Once the filter insert unit <NUM> has been inserted into the recess <NUM> of the filter <NUM>, the outer surface of the filter <NUM> may be squeezed in the direction shown by the mutually facing arrows. The pressure thereby applied to the adhesive on the outer surface of the filter insert unit <NUM> is such as to cause the adhesive to bond the filter <NUM> to the filter insert unit <NUM>. Alternatively, adhesive may be applied to the outer surface of the insert unit <NUM> as shown in <FIG>. The adhesive may be applied in one or more radially disposed strips <NUM> which extend the length of the filter insert unit <NUM>. Prior to use the strips may be covered by a protective cover which is removed immediately before insertion of the filter insert unit <NUM> into the recess <NUM> of the filter <NUM>. The adhesive strips <NUM> then adhere the filter insert unit <NUM> to the inside of the recess <NUM> of the filter <NUM>.

While the filter insert unit <NUM> described above may be formed from filtration material such as cellulose acetate, other materials may alternatively be employed.

For example, the filter insert unit <NUM> may be formed from wax or a similar substance. Once inserted, the insert unit <NUM> may melt slightly due to heat transferred from the distal end <NUM> of the smoking article <NUM> shown in <FIG>, during smoking. The filter insert unit <NUM> may thus be adhered to the inner surface of the recess <NUM> of the filter <NUM>. The slight melting of the wax may also aid the release of flavourants and fragrances contained within the filter insert unit <NUM>.

<FIG> shows an alternative filter insert unit <NUM> in capsule form formed from gelatine or other substances with similar physical properties. Such a filter insert unit <NUM> may be arranged to adopt the shape of the recess <NUM> once it is inserted therein. The filter insert unit <NUM> in capsule form may be frangible so that it bursts and releases its contents when the filter insert unit <NUM> has been inserted and the filter <NUM> squeezed.

While the filter insert unit <NUM> described above with reference to <FIG> is intended for insertion in a recess <NUM> which is circular in end-on cross-section, as shown in <FIG>, recesses of different cross-sectional shapes may also be used. <FIG> is an end-on view showing the buccal end <NUM> of a filter <NUM> of a smoking article <NUM>. The outline of the recess <NUM> as viewed end-on is irregular and an insert unit <NUM>, when viewed end-on, is complementary in shape to achieve a secure fit. Irregular end-on cross-sectional shapes such as that shown in <FIG> are advantageous since they increase the surface area of the interface between the filter insert unit <NUM> and the filter <NUM>.

<FIG> shows a filter <NUM> and a filter insert unit <NUM> according to a further example. In this example, the filter insert unit <NUM> is provided with a spike <NUM>. The spike <NUM> may comprise one or more barbs <NUM>. When the filter insert unit <NUM> is inserted into the recess <NUM> of the filter <NUM> the spike <NUM> and barbs <NUM> become at least partially embedded within the cylindrical filtration region <NUM> of the filter <NUM> which assists in retaining the filter insert unit <NUM> in the filter <NUM>.

In a further example shown in <FIG>, the filter insert unit <NUM> comprises an outer screw thread <NUM> arranged around the outer surface of the filter insert unit <NUM>. The recess <NUM> of the filter <NUM> may also comprise an inner screw thread <NUM> arranged along the inner surface of the recess <NUM>. As the filter insert unit <NUM> is inserted it may be twisted such that the outer screw thread <NUM> and inner screw thread <NUM> engage so that the filter insert unit <NUM> may be retained inside the recess <NUM> of the filter <NUM>.

The screw threads <NUM>, <NUM> may be provided as a moulded or extruded filler material or plastic. Alternatively, the screw thread may be formed by embossing the inner surface of the recess <NUM> and/ or the outer surface of the filter insert unit <NUM>, for instance in the case that the recess is formed by a stiff paper or card-like material which can be embossed, or where a plug wrap surrounding the filter insert unit <NUM> can be embossed. The screw threads <NUM>, <NUM>, in some examples, may be provided in one or other but not both of the filter insert unit <NUM> and recess <NUM>, providing channels between the screw threads along which smoke may pass in use.

In a further example, a filter insert unit <NUM> may be inserted into the recess <NUM> through an opening located along the side of the filter <NUM> as shown in <FIG> shows a filter <NUM> according to such an example. A downstream cylindrical filtration region <NUM>, an intermediate tubular filtration region <NUM> and an upstream cylindrical filtration region <NUM> are located end to end as shown in <FIG>. The intermediate tubular filtration region <NUM> has a portion cut away to allow insertion of the filter insert unit <NUM> therein. Plugwrap, tipping paper, or any other suitable wrapper that may be used to hold the downstream cylindrical filtration region <NUM>, the intermediate tubular filtration region <NUM> and the upstream cylindrical filtration region <NUM> in place may also have a cutaway portion to allow insertion of the filter insert unit <NUM> into the recess <NUM>. In use, the downstream cylindrical filtration region <NUM> retains the filter insert unit <NUM> in place inside the filter <NUM>.

<FIG> shows an example where a filter insert unit <NUM> is inserted into a sleeve <NUM>. The sleeve <NUM> comprises a cylindrical region <NUM> of filtration material such as cellulose acetate having a recess <NUM> extending part of the length of the cylindrical region <NUM> from an upstream end of the cylindrical region <NUM>. The sleeve <NUM> further comprises a sleeve portion <NUM> which may consist of a rigid card overwapper longer than the cylindrical region <NUM> so that a smoking article may be inserted into the hollow area defined by the sleeve portion <NUM>. In use, a filter insert unit <NUM> may be inserted into the recess <NUM> before the sleeve is placed over a smoking article so that the sleeve portion <NUM> overlies the mouth end of the smoking article. As such, the sleeve <NUM> retains the filter insert unit <NUM> in place during use.

<FIG> shows an example where the insertable filter unit is a spike <NUM> which may be inserted into a conventional smoking article filter. The spike <NUM> may be formed from a material comprising plastic, wood or any other suitable material. The spike <NUM> may have an additive such as a flavourant, or sorbent applied thereto to impart an organoleptic quality to smoke passing through a filter. <FIG> are end-on views of a filter <NUM> showing the buccal end <NUM> having a filter insert unit <NUM> inserted therein according to respective examples. In these examples the filter insert unit <NUM> and the recess <NUM> of the filter <NUM> have different cross-sectional shapes when viewed from the rear. <FIG> shows a filter insert unit <NUM> having a circular cross section inserted into a recess <NUM> having a triangular cross section. <FIG> shows a filter insert unit <NUM> having a circular cross section inserted into a recess <NUM> having a square cross section. <FIG> shows a filter insert unit <NUM> having a square cross section inserted into a recess <NUM> having a circular cross section. As may be seen from <FIG>, using differently shaped filter insert units <NUM> and recesses <NUM> allows the formation of channel <NUM>. The number and shape of such channels <NUM> may be varied by varying the combination of the shapes of the filter insert units <NUM> and recesses <NUM> as may be seen by when comparing <FIG>. Such variation in shape may also lead to a compressive fit between the filter <NUM> and the filter insert unit <NUM> which can assist in retaining the filter insert unit <NUM> therein. It should be borne in mind that other combinations of shapes of filter insert unit <NUM> and recess <NUM> than those shown in <FIG> may be employed.

<FIG> shows a filter insert unit <NUM> according to a further example. The filter insert unit <NUM> according to this example comprises a bulk of filtration material <NUM> such as cellulose acetate having several grooves <NUM> extending along at least part of the length of and on a peripheral region of the filter insert unit <NUM>. The filter insert unit <NUM> is wrapped using a plugwrap or other suitable wrapper. The wrapper may comprise perforations to allow a certain amount of smoke to pass therethrough, the perforations for instance coinciding with the grooves <NUM>. The filter insert unit <NUM> may be provided with a second wrapper <NUM> which does not follow the contours of the peripheral grooves <NUM> so that channels are defined between the second wrapper and the bulk of the filtration material, as shown in <FIG>. In use, when the filter insert unit <NUM> of <FIG> is inserted into a recess <NUM>, smoke may pass through the perforations in the plug wrap of the filter insert unit <NUM> providing a unique smoking experience. <FIG> shows a filter insert unit <NUM> according to an example where no second wrapper <NUM> is used.

As an alternative to the example shown in <FIG>, the grooves may be provided as helical, peripheral grooves to provide a modified smoke delivery route.

<FIG> shows an example where the filter insert unit <NUM> comprises a cylindrical part <NUM> and a tubular part <NUM>. The cylindrical part <NUM> may be formed from filtration material such as cellulose acetate. The tubular part <NUM> may be formed from card although other materials may be used. The outer surface of the cylindrical part <NUM> and the inner and outer surfaces of the tubular part <NUM> may be provided with barbs so that the cylindrical part <NUM> may be retained within the tubular part <NUM> and so that the tubular part <NUM> may be retained within the recess <NUM> of a filter <NUM>.

<FIG> shows a filter insert unit according to an embodiment of the invention. Filter insert unit <NUM> comprises thin insertable part <NUM>, arranged to be inserted into a recess <NUM>, and a thicker non-insertable part <NUM>. Both parts <NUM>, <NUM> may be formed from any of the materials hereinbefore described.

<FIG> shows a filter insert unit <NUM> similar to the filter insert unit <NUM> shown in <FIG> except that the filter insert unit <NUM> further comprises a sleeve <NUM> arranged to fit over the outer surface of a filter <NUM>. The sleeve <NUM> may be formed from any suitable material such as paper or card.

<FIG> shows a filter <NUM> according to a further example. The filter <NUM> comprises two recesses <NUM>. Each recess <NUM> may have a filter insert unit <NUM> inserted therein. In alternative examples, more than two recesses may be provided. As used in the foregoing description, the term smoking article includes smokable products such as cigarettes, cigars and cigarillos whether based on tobacco, tobacco derivatives, expanded tobacco, reconstituted tobacco or tobacco substitutes and also heat-not-burn products.

Embodiments of the invention are configured to comply with applicable laws and/ or regulations, such as, by way of non-limiting example, regulations relating to flavours, additives, emissions, constituents, and/ or the like. For example, the invention may be configured such that a smoking article implementing the invention is compliant with applicable regulations before and after use/ manipulation by a user.

Claim 1:
An insertable filter unit (<NUM>) for a smoking article filter (<NUM>), the insertable filter unit (<NUM>) comprising a retaining means to retain the insertable filter unit (<NUM>) in a recess in the smoking article filter (<NUM>), the insertable filter unit (<NUM>) having a thin insertable part (<NUM>) arranged to be inserted into the recess and a thicker non-insertable part (<NUM>), and wherein the insertable filter unit (<NUM>) comprises a smoke modifying substance comprising a flavourant comprising tobacco, and filtration material.