Patent Description:
So called "Actron" type tobacco smoke filters are well known (e.g. see <CIT> and <CIT>).

These include a core of thermoformed cellulose acetate material which includes part-length external grooves, and a non-porous core wrapper which follows the profile of these grooves. The filter includes a ventilated outer wrapper which allows ventilating air to enter the external grooves and flow along the external grooves into the mouth of the smoker, along with smoke which is drawn through the core of cellulose acetate material. The non porous core wrapper prevents ventilating air from entering the cellulose acetate core and there is, therefore, no mixing of air and smoke in the filter. These filters are prone to crushing of the ventilated outer wrapper into the grooves (e.g. during cigarette manufacture and/or by the mouth of the smoker in use). Further, the so-called "air and smoke" effect caused by the lack of mixing of air and smoke in the filter may lead to an inferior taste sensation.

Other filters with a grooved wrap or profile can also suffer from crushing during processing and handling.

There is a need for a tobacco smoke filter which does not have these disadvantages.

According to the present invention there is provided a tobacco smoke filter element as defined in claim <NUM>.

Herein the term "downstream" means towards the end of the filter/filter element/filter cigarette which is closest to the mouth of the smoker of a filter cigarette (e.g. when the filter/filter element is attached to a tobacco envelope in a filter cigarette). The term "upstream" means towards the end of the filter/filter element which is closest to the tobacco envelope of the filter cigarette (e.g. when the filter/filter element is attached to a tobacco envelope in a filter cigarette).

Herein, the term "thermoformed core" means a core which has been shaped or moulded into a coherent, self supporting, core using the action of heat on the tobacco smoke filtering material (and optional other components such as plasticiser).

According to the disclosure there is provided a tobacco smoke filter element comprising a (longitudinally extending) thermoformed core of tobacco smoke filtering material having a profiled outer surface which includes at least one longitudinally extending groove which extends (e.g. continuously) the (full) length of the thermoformed core. The profiled (e.g. corrugated) outer surface of the (thermoformed) core may include from one to sixteen longitudinally extending grooves (preferably <NUM> to <NUM> grooves, e.g. <NUM> to <NUM> grooves) which extend (e.g. continuously) along the thermoformed core (along the full length of the core).

The filter element may further comprise a stiff outer wrapper engaged around the (longitudinally extending) thermoformed core of tobacco smoke filtering material. The profiled (e.g. grooved e.g. corrugated) outer surface may therefore define with the (inner surface of the) stiff outer wrapper at least one (e.g. covered) longitudinally extending channel which extends (e.g. continuously) the (full) length of the core (formed by the stiff outer wrapper covering the groove(s) in the outer surface of the core).

Preferably the stiff outer wrapper comprises a stiff paper, for example a stiff plugwrap paper. The stiff outer wrapper may be a paper (e.g. plugwrap paper) of basis weight from about <NUM> to <NUM> gsm. The stiff outer wrapper may be a paper (e.g. plugwrap paper) of lighter weight, for example of basis weight <NUM> to <NUM> gsm, to which additives have been applied to make it stiff, as well known in the art. Stiff papers, for example stiff plugwrap papers, are well known in the art.

Preferably the thermoformed core does not include a further wrapper (e.g. air impermeable wrapper) following the profiles of (for example adhering to) the profiled outer surface. In other words it is preferred that there is no further wrapper between the profiled outer surface of the core and the inner surface of the stiff outer wrapper (if present). Preferably the thermoformed core is a core comprising a coherent, bonded, (smoke-permeable) material (e.g. cellulose acetate). Herein the term coherent means self supporting; the coherent bonded thermoformed core material holds its shape and profiled surface without requirement for a shaped wrapper (to hold it in shape). Suitable materials for the thermoformed core are as described above for the downstream thermoformed core.

The total cross-sectional area of the longitudinally extending channels/grooves may amount to between <NUM> and <NUM>%, preferably at least <NUM>%, more preferably between <NUM> and <NUM>%, of the overall cross-sectional area of the (downstream) thermoformed core of the filter. Careful control over the number and/or depth of the channels (e.g. determined by the thermoforming process which the downstream core is made) may give improved filtering performance and/or sensory characteristics. This may be achieved by increasing the depth of the corrugations, preferably with increase in surface area of the corrugations, and optionally along with increase in the corrugation pitch - that is widening of the corrugations with reduction in their number. For example, a filter according to the invention may have five channels which are about <NUM> deep and at a pitch of about <NUM>.

According to the disclosure in a further aspect there is provided a multiple rod comprising a plurality (e.g. <NUM>, <NUM>, <NUM> etc.) of filters (or filter elements) as described above and/or herein integrally 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 <NUM> schematically illustrates a filter not according to the invention; and <FIG> shows the downstream end view of a filter according to the invention.

FIGURE1 shows a tobacco smoke filter <NUM> of length <NUM> and circumference around <NUM> which includes a stiff outer wrapper <NUM> (shown by the dotted line) of stiff plugwrap paper of basis weight <NUM> gsm. The stiff outer wrapper is engaged around a downstream longitudinally extending thermoformed core <NUM> of tobacco smoke filtering material of length <NUM>; and a longitudinally extending substantially cylindrical further core <NUM> of tobacco smoke filtering material, also of length <NUM>. The further core <NUM> is longitudinally aligned with the thermoformed core <NUM> and the downstream end of the further core <NUM> is abutted to the upstream end of the downstream thermoformed core of tobacco smoke filtering material. The stiff outer wrapper includes ventilation (not shown).

The downstream thermoformed core <NUM> is formed from cellulose acetate tow to which a glyceryl triacetate plasticiser has been applied. The core <NUM> is formed in a multiple length of cores by continuously drawing and/or gathering a flow of tobacco smoke of cellulose acetate tow bearing plasticiser through a shaped die to form an advancing multiple length of cores with profiled outer surface, and heat treating the advancing multiple length of cores as and/or or shortly after it is formed (with a subsequent cooling step) by methods similar to those disclosed in <CIT>. The heat treatment and cooling activates the plasticiser to form the cellulose acetate material into a multiple length of coherent, bonded, smoke-permeable downstream thermoformed cores having profiled (e.g. grooved e.g. corrugated) outer surface. The multiple length of cores is then cut down to single cores <NUM> during filter or cigarette formation by methods well known in the art.

The downstream thermoformed core <NUM> has a profiled outer surface which includes four longitudinally extending grooves <NUM>. Each groove <NUM> defines with the inner surface of the stiff outer wrapper a longitudinally extending channel (which is covered by the wrapper <NUM>), which extends continuously the full length of downstream core <NUM>.

The further core <NUM> is a non-wrapped substantially cylindrical core of cellulose acetate, for example such as a non wrapped acetate (NWA) filter segment, such as is well known in the art.

It will be appreciated that filters such as those illustrated in Figure <NUM> may be made by methods well known in the art, by for example by longitudinally advancing a continuous flow of component multiple (e.g. dual) filter rods (arranged appropriately, e.g. with dual component rods which will form the downstream cores <NUM> located between dual component rods which will form the further cores <NUM>) to a wrapping garniture where the continuously advancing stiff outer wrapper is wrapped around the longitudinally advancing flow of component multiple filter rods and fixed using a lapped and stuck seam (as is well known). The wrapped longitudinally advancing flow of component multiple filter rods is then cut appropriately for further use, by methods well known in the art.

The filter <NUM> is joined to a wrapped tobacco rod <NUM> with the upstream core <NUM> towards the tobacco. The filter <NUM> is joined to the wrapped tobacco rod 6by ring tipping [which engages around just the adjacent ends of the (wrapped) filter and rod to leave much of the stiff wrapper <NUM> exposed], by methods which are well known in the art.

The applicants have found that the combination of the profiled thermoformed downstream core and the stiff outer wrapper gives better end definition than previous comparable products, because the covered channels are not crushed or distorted during the subsequent processes of filter and filter cigarette manufacture and use; this is useful for anti-counterfeit purposes. The thermoformed core is coherent and self supporting and therefore does not require a further wrapper (e.g. air impermeable wrapper) which follows the profiles of the profiled outer surface; this may result in improved smoking qualities (e.g. by reducing or negating the "air and smoke" effect) because ventilating air may enter the downstream core through the ventilation and/or longitudinally extending channels.

In a further example (not shown), a tobacco smoke filter similar to that illustrated in Figure <NUM> includes a further NWA core which is coloured or tinted red (e.g. using appropriate dyes or pigments with regulatory approval for use in food contact applications), and the downstream thermoformed core comprises white cellulose acetate (as in Figure <NUM>). It will be appreciated that in this example the red colour of the further core will contrast with, and therefore be visible at the upstream end of the longitudinally extending channel(s) in, the downstream thermoformed core, when the downstream end of the downstream core is viewed "end on" along the longitudinal axis of the filter/element. This contrast provides a product filter, element or rod with an enhanced distinctive appearance that is useful for anti-counterfeit purposes.

<FIG> shows the downstream end view of an embodiment of the invention. In this embodiment, tobacco smoke filter <NUM> of length <NUM> and circumference around <NUM> includes a stiff outer wrapper <NUM> (shown by the bold line) of stiff plugwrap paper of basis weight <NUM> gsm. The stiff outer wrapper is engaged around a downstream longitudinally extending thermoformed core <NUM> of tobacco smoke filtering material of length <NUM>; and a longitudinally extending substantially cylindrical further core of tobacco smoke filtering material, also of length <NUM> (not shown). The further core is longitudinally aligned with the thermoformed core <NUM> and the downstream end of the further core is abutted to the upstream end of the downstream thermoformed core <NUM> of tobacco smoke filtering material. The stiff outer wrapper includes ventilation (not shown).

The downstream thermoformed core <NUM> defines a further channel or bore <NUM> of circular cross section which extends longitudinally through the downstream thermoformed core. The bore <NUM> extends through the downstream thermoformed core from the downstream end to the upstream end. As seen in <FIG>, bore <NUM> extends through the centre of the downstream thermoformed core (that is, along the central axis of the core). As shown in <FIG> (although not to scale), there is at least <NUM> of thermoformed material between the periphery of the bore <NUM> and the closest part of the profiled outer surface of core <NUM>.

The downstream thermoformed core <NUM> is formed from cellulose acetate tow to which a glyceryl triacetate plasticiser has been applied, in a similar manner to that used to form thermoformed core <NUM> of the example of Figure <NUM>.

The further core (not shown) is a non-wrapped substantially cylindrical core of cellulose acetate, for example such as a non wrapped acetate (NWA) filter segment, such as is well known in the art.

The filter <NUM> may be joined to a wrapped tobacco rod with the upstream core towards the tobacco. The filter is 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 stiff wrapper <NUM> exposed], by methods which are well known in the art.

Claim 1:
A tobacco smoke filter element (<NUM>) comprising a thermoformed core (<NUM>) of tobacco smoke filtering material having a profiled outer surface which includes at least one longitudinally extending groove (<NUM>) which extends the length of the thermoformed core; wherein the thermoformed core does not include a further wrapper following the profile of the profiled outer surface; wherein the thermoformed core defines one or more further channels or bores (<NUM>) which extend longitudinally through the thermoformed core and wherein there is at least <NUM> of thermoformed material between the further channels or bores and the closest part of the profiled outer surface.