HK1058886B - Recess filter and smokeable article containing a recess filter - Google Patents

Description

Recess filter and smokeable article comprising a recess filter

Technical Field

The invention relates to a recess filter (Reze β fi1ter), a filter rod consisting of a plurality of such recess filters, and a smokeable article, in particular a cigarette or cigarillo, containing one such recess filter.

Background

Cigarettes with recess filters or with blank segments have been known for a long time. One such cigarette, for example, the russian cigarette (papyrissies), has a completely empty mouth section that tends to collapse or twist before or during use. In another such cigarette, one or more filter elements are provided at the tobacco-side end of the mouth piece in addition to the mouth-side cavity.

In GB 2210546 a, cigarettes with recess filters are described, with and without filter elements, in which the cavity wall has perforations for influencing the ambient air and is designed such that it can be compressed in the longitudinal direction after use, in order thereby to reduce the waste volume. For this purpose, the cavity wall is, for example, designed as a spiral.

An example of an unventilated cigarette with recess filter is known from DE-AS 1056023. However, ventilation of the filter is necessary because the current trend is to make the cigarette easier to smoke.

WO 00/00047 discloses an example of a ventilated cigarette with recess filter. The gas-impermeable cavity wall surrounds the entire filter segment, i.e. the cavity and the filter element. Venting is achieved by using a mechanically perforated cavity wall surrounded by a thin facing layer that is likewise perforated. In order to achieve high perforation rates of up to 90%, additional perforations are made through the face paper, the cavity wall and the filter sleeve by means of an in-line laser during the cigarette production process.

WO 00/00047 therefore describes two of the three methods currently used to produce ventilated cigarettes with recess filters. I.e. one is in-line laser perforation. However, this method has the disadvantage of being very expensive, since special production facilities have to be provided, and special safety measures have to be taken with these facilities. Furthermore, the maximum perforation rate can only be about 65% by in-line laser perforation.

A second method is to mechanically perforate the material of the cavity wall, for example with a needle, before cigarette production. In this case a relatively large hole is produced. This perforated material is then combined with a plain paper facing, i.e. with a paper facing having relatively small holes, which is also perforated beforehand. These superposed perforated layers cannot be bonded to each other and are therefore very easily movable relative to each other. As a result, the smaller holes of the facing paper and the larger holes of the cavity wall do not always overlap each other completely or partially. Thus undesirably resulting in relatively large ventilation variations and irregularities. Furthermore, even in the case of mechanical perforation, the highest ventilation levels can only be about 50 to 55%, since perforations of any size are not possible in order to maintain the stability of the cavity wall. As a result, as is known from WO 00/00047 discussed above, the two methods, i.e. laser perforation on-line and mechanical perforation in advance, must be combined with each other in order to achieve a high degree of ventilation, which results in an overall process that is definitely extremely expensive and complicated, while at the same time the problem of varying degrees of ventilation is not solved thereby.

A third current approach is to use cavity walls that are inherently air permeable. The aim is then here to achieve ventilation. The necessary perforation of the cavity wall is eliminated. However, disadvantages are that such air-permeable cavity wall materials are very expensive and have a significantly reduced stability when subjected to moisture, for example by smoke flow or the lips of a smoker, and that the cavity is compressed in an undesirable manner or may collapse completely during use.

Disclosure of Invention

It is therefore an object of the present invention to provide a ventilated recess filter and a ventilated smokable recess filter article which can be produced conveniently and using conventional pre-perforated lamina layers. These products should be designed in particular to have a high degree of ventilation, without causing significant variations in the relative degree of ventilation.

To this end, a smokeable article, in particular a cigarette or cigarillo, is made comprising:

-a tobacco column surrounded by cigarette paper and/or one or more tobacco sheets, and

-a ventilated recess filter, wherein the tobacco column and the recess filter are interconnected by an at least partially air-permeable thin face layer, and wherein

The recess filter has one or more (preferably successive) filter elements at the tobacco-side end of the recess filter and a tubular cavity at the mouth-side end of the recess filter,

preferably each filter element is surrounded by a filter sleeve, an

The cavity is surrounded by a (tubular) cavity wall,

it is characterized in that:

at least one filter element, preferably the filter sleeve present, is at least partially air-permeable;

-the ventilation of the recess filter is at least 10%;

the cavity wall preferably has a porosity of 100Coresta units or less and is free of perforations;

the cavity wall surrounds only the cavity or does not completely surround the cavity and the filter elements and preferably in such a way that, at least at the tobacco-side end of the recess filter, one filter element is at least partially not surrounded by the cavity wall;

-the length of the cavity is 10mm or less than 10 mm; and

-the ratio of the length of the cavity to the total length of the recess filter (including the length of the cavity) is 0.3 or less than 0.3, and having a recess filter for smokeable articles comprising:

-one or more filters on a first end of the recess filter,

-a tubular cavity on the second end of the recess filter;

preferably a filter sleeve surrounding each filter element, and

a (tubular) cavity wall surrounding the cavity,

it is characterized in that:

at least one filter element, preferably the filter sleeve present, is at least partially air-permeable;

-the ventilation of the recess filter is at least 10%;

the cavity wall preferably has a porosity of 100Coresta units or less and is free of perforations;

the cavity wall only surrounds the cavity, or does not completely surround the cavity and the filter elements in such a way that at least at the first end of the recess filter one filter element is at least partially not surrounded by the cavity wall;

the cavity wall and the filter element with its preferably present filter sleeve are surrounded by an at least partially gas-permeable, communicating envelope;

-the length of the cavity is 10mm or less than 10 mm; and

the ratio of the length of the cavity to the total length of the recess filter (including the cavity length) is 0.3 or less than 0.3.

Common materials for the veneer layer may be used, such as white cork, gold or aluminium foil, imitation cork paper, straw, silk or rose petals. The thin facing layer used is at least partially perforated at the time of its production and is thus sufficiently air-permeable in order to cause the desired ventilation of the filter.

Conventional materials can be used for tobacco, cigarette paper and tobacco sheet. For example, any tobacco blend may be used.

The filter element used is preferably a conventional filter sleeve. It can be made of paper which has a natural porosity so as to ensure sufficient air permeability. But non-porous filter sleeves may also be used. However, since the ambient air should pass from the outside into the filter element or filter elements, it is important that the filter sleeve, which is preferably present in at least one filter element, is at least partially sufficiently air-permeable, so that, for example, ambient air can enter the filter sufficiently from the side in those places where the filter element with the air-permeable filter sleeve is not surrounded on its outside by a preferably air-impermeable cavity wall.

Preferably, the filter elements are of circular or elliptical cross-section, in other words they are cylindrical or elliptical-cylindrical.

All customary filter materials can be used as filter elements, for example fibrous, such as cotton, paper, crepe paper, cellulose acetate, plastic fibers (e.g. polypropylene plastics) or cellulose acetate, or granular, such as silica gel, aqueous polysilicates, activated china clay or activated carbon, all of which may optionally contain fragrances.

One or more filter elements may be used. If the least possible amount of condensate should be obtained or if granular filter elements should be used, it is advantageous to use a plurality of, for example two, filter elements. Any known filter construction may be used for filtration, that is to say for example double or triple filters. The dual filter may for example consist of a filter on the mouth side made of cellulose acetate, followed by a paper filter or an activated carbon filter. Triple filters may, for example, consist of a cellulose acetate filter on the mouth side followed by an activated carbon filter, to which a cellulose acetate filter is connected. Yet another possible combination is a filter comprising a central cavity. I.e. filter-cavity-filter.

Examples of materials for the cavity wall are paper, cardboard or also plastics, which are preferably biodegradable. The cavity walls must be of sufficient thickness to ensure stability during the smoking process. For example, a weight per unit area of > 80g/m can be preferably used²Of paper, in particular 90 to 120g/m²And particularly preferably about 110g/m²And a thickness of > 80 μm, in particular 100-. Such paper may be composed of common ingredients (e.g., strong pulp (about 87.5 wt%), inorganic filler (about 5 wt%), starch slurry (0.5 wt%) and moisture (about 7 wt%).

The cavity of the smokable article or recess filter should be up to 10mm long, preferably only 6mm long or less, for stability. Preferably, this cavity is 4 to 6mm long, with a total length of the recess filter of typically 20 to 40mm and especially 25mm to 31.5 mm.

The cavity wall is preferably gas impermeable, that is to say it has a gas permeability (or permeability) of 100Coresta units or less, preferably 10Coresta units or less, particularly preferably about OCoresta units. Ambient air can thus enter the filter from the outside, via the pre-perforated thin face layer and the preferably present communicating envelope and filter sleeve, where it is not surrounded by the cavity wall and ensures the necessary ventilation. The cavity walls themselves may also be breathable or perforated. This is not preferred, however, since taking such measures generally increases the material price and increases the production difficulty, and the additional perforation or breathability downstream of the cavity-free walls, preferably at the end of the filter on the tobacco side, is not of significance for practical use.

The diameter of the smokeable article is 7.6 to 8.4mm for normal cigarettes and 5.0 to 7.6mm for fine or fine cigarettes.

The air permeability can be adjusted according to the permeability of the filter sleeve, the communicated envelope and the surface paper. The ventilation should be at least 10% (this corresponds generally to a condensate content of the cigarette smoke of 12 to 14mg), but better still at least 40% (corresponding to a condensate content of about 6 to 8mg), preferably at least 60% (corresponding to a condensate content of less than about 4mg), and particularly preferably at least 75% (corresponding to a condensate content of about 1 to 2 mg). However, the product according to the invention can also have an air permeability of 90% and more, for example 95%, and a condensate content of less than about 1 mg.

It is particularly advantageous here that the product according to the invention allows high and very high permeabilities (for example > 90%) to be achieved without the need to combine different methods as in the prior art, with no major variations in the degree of ventilation associated therewith, in other words it allows a relatively stable ventilation.

To do this, the cavity wall surrounds only the cavity itself or a portion of the cavity wall and one or more filter elements. For example, in a double filter embodiment, the cavity wall can surround the mouth-side filter element in addition to the cavity itself, but not or only partially the tobacco-side filter element. As an alternative to this embodiment, the cavity wall surrounds the cavity itself and the tobacco-side filter element but not the mouth-side filter element located between them, in an embodiment with a triple filter, for example, the cavity and the mouth-side filter element can be surrounded by the cavity wall but not the central and tobacco-side filter element. Other alternatives are also conceivable for this embodiment, for example a filter element with a cavity wall around the mouth side and in the center. (of course, the end sides of the filter element are neither surrounded by cavity walls nor by the filter sleeve). Thus, when the cigarette is used, ventilation air can enter the recess filter through the outer paper facing, the optionally present connected wrapping and the filter sleeve in the region not surrounded by the cavity wall. Here, the degree of ventilation can be adjusted by the porosity of the material used. For this purpose, the filter sleeve, if present, the connected envelope, if present, and the outer surface paper are at least partially air-permeable, i.e. have an air permeability of more than 100Coresta units, preferably 200Coresta units or more, in particular 1000Coresta units or more, preferably 10000 to 2000Coresta units or more (for example up to 30000), in particular about 12000Coresta units. Here, the air permeability depends on the desired ventilation. Of course, these different garments need not have uniform air permeability, but the lowest air permeability in the different garments determines the air permeability. Conventional materials may be used for such outer sleeves, which are either inherently sufficiently porous to have the necessary air permeability (e.g. conventional paper filter sleeves), or may be perforated prior to use, e.g. by laser or spark perforation of a thin facing layer. The necessary perforations or porosity may be provided along the entire surface of these outer sleeves; it is only necessary where adequate ventilation is to be ensured, i.e. where the filter element or elements are not surrounded by a preferably gas-impermeable cavity wall. In addition, it is also conceivable, when a plurality of filter elements are present, for both filter elements to be surrounded by a gas-permeable filter sleeve. Alternatively, one of the two filter elements can be surrounded by an air-permeable casing and the other by an air-impermeable filter sleeve, i.e. a filter sleeve having an air permeability of 100Coresta units or less.

The production of the products according to the invention can be carried out in different ways. For example, a filter element (or two or more filter elements) may employ an air-permeable filter sleeve. The filter itself (with or without the filter sleeve) may then be combined with the tubular cavity wall by enclosing a communicating envelope, thereby obtaining a recess filter. The recess filter can be coupled in the usual manner to a tobacco column which is produced separately and is already wrapped in cigarette paper or tobacco sheet, by means of a pre-perforated lamina layer at a filter mounting machine. The use of interconnected envelopes is not absolutely necessary here. The filter elements, which are optionally wound with a filter sleeve, can also be connected directly to the filter tip attachment machine by a thin surface layer at one end to the tubular cavity wall and at the other end to the tobacco column.

Where two or more filter elements are used (e.g. a combination of a cellulose acetate filter and an activated carbon filter), one of which is surrounded by a cavity wall, there may be two different production processes, both of which result in a consistent product and both of which may be carried out continuously.

In a first method, a first filter rod (Filterpropfen) is first produced in the wall of the tubular cavity. These filter rods have twice the length of the first (mouth-side) filter of the finished recess filter and are arranged at a distance from one another which is equal to twice the length of the cavity. The rod is now cut open at its centre and the resulting segment is combined with a second filter rod twice as long as the second (tobacco-side) filter in the finished recess filter by wrapping a communicating envelope. The strip thus obtained is then cut centrally on every second filter rod, so as to form a hidden filter strip having four times the length of the finished hidden filter. (alternatively, a cut may be made in the center of every third second filter rod, thus obtaining a recessed filter strip having six times the length of the finished recessed filter.)

This intermediate product is obtained in a second production method in that the cavity wall is fixed in an open manner, for example by gluing, to the unsealed connecting envelope. Wherein a distance is maintained between the two cavity walls, which distance is equal to twice the length of the tobacco-side filter element in the finished recess filter. In a further step, a filter rod is placed between the open cavity walls and, connected to the end faces thereof, a filter element is placed on the cavity walls, which filter element corresponds to the filter element on the mouth side of the finished recess filter. The walls of the bonded cavity and the connected envelope are then closed, for example, and the resulting strip is cut centrally through each second filter rod, thereby still obtaining a concealed filter strip.

The hidden filter rod obtained according to one of the two above-described methods is cut centrally at the filter tip attachment machine, so as to form two shorter rods each containing two finished hidden filters, in the order tobacco-side filter, mouth-side filter, cavity (with the length of the cavity being twice that of the finished hidden filter), mouth-side filter and tobacco-side filter. The short filter rod consisting of the two recess filters is now placed on a filter mounting machine and connected at both ends to the tobacco column by means of a paper facing, and the resulting product is then cut again in the center, so that the finished cigarette is obtained.

Drawings

Embodiments of the invention are illustrated in the drawings and described in detail below. Wherein:

FIG. 1 is a cross-sectional view through a recess filter comprising a filter element according to the present invention and a tobacco column partially attached thereto;

FIG. 2 is a cross-sectional view through a recess filter and partially attached tobacco column including two filter elements according to the present invention;

FIG. 3 is a cross-sectional view through a recess filter comprising two filter elements and a tobacco column partially attached thereto according to the present invention;

figures 4 and 5 are two schematic views of a recessed filter strip manufactured with four times the length of the finished recessed filter; and

figure 6 shows the production of a cigarette with a recess filter.

Detailed Description

Figure 1 shows a cigarette 10 comprising a tobacco column 12, which shows a portion, and a cigarette paper 14, which surrounds the exterior. There is seen a recess filter 20 which is joined to the tobacco column 12 by a thin face layer 16. The recess filter 20 has only one cellulose acetate filter element 22, which is surrounded by a gas-permeable filter sleeve 28. This filter element 22 is connected to a gas-impermeable cavity wall 32 by a connecting envelope 34, the cavity wall 32 itself surrounding the cavity 26. In use of the cigarette 10, ambient air can enter the filter 20 from the side through the air-permeable face paper 16, the air-permeable communication envelope 34 and the air-permeable filter sleeve 28, and thus ensure the necessary ventilation without causing significant ventilation changes.

Figure 2 shows another embodiment of a cigarette 10 with a recess filter. It can be seen that there is still a column of tobacco 12 surrounded by cigarette paper 14 and joined to the recess filter 20 by the face paper 16. Here, the recess filter 20 has two filter elements, namely a first filter element 22 and a second filter element 24. The first filter element 22 is surrounded by a gas-impermeable filter sleeve 28, whereas the second filter element 24 is surrounded by a gas-permeable filter sleeve 30. The two filter elements 22 and 24 are in turn coupled by a communicating envelope 34 to a gas-impermeable cavity wall 32 surrounding the cavity 26. During smoking of the cigarette 10, ventilation air can only enter the second filter element 24, since, due to the impermeability of the filter sleeve 28 and the cavity wall 32, ambient air cannot enter the first filter element 22 and the cavity 26 from the side. Of course, as an alternative, the reverse form may also be selected, i.e. the filter element 24 has a gas-impermeable filter sleeve 30, and the filter element 22, on the contrary, has a gas-permeable filter sleeve 28. Alternatively, both filter sleeves 28 and 30 are air permeable.

Finally, figure 3 shows another embodiment of a cigarette 10 with a recess filter. In this embodiment, in addition to the tobacco column 12, cigarette paper 14, recess filter 20, connected envelope 34 and face paper 16, there are two filter elements, namely a first filter element 22 and a second filter element 24. The filter sleeve 28 of the first filter element 22 may be gas-permeable or gas-impermeable. This is not critical, since in this embodiment, lateral ingress of ambient air into the first filter element 22 is prevented by the air-impermeable cavity wall 32 which surrounds both the first filter element 22 and the cavity 26. The filter sleeve 30 of the second filter element 24 is therefore highly permeable, so that sufficient ventilation through the second filter element 24 is ensured during smoking of the cigarette 10. In a further variant of the embodiment shown, the cavity wall 32 does not completely surround the first filter element 22, but only partially.

Figures 4 to 6 show the production possibilities of cigarettes with recess filters. A first possibility of producing the concealed filter strip 40 is first shown in fig. 4. To this end, in a first step, the first filter rod 23 is continuously wrapped in a machine into an air-impermeable cavity wall 38, the filter rod 23 having twice the length of the first (mouth-side) filter element 22 in the finished recess filter and being surrounded by a wrapping paper 29 (also twice the length of the filter sleeve 28). For the first step of fig. 4, it can be seen that the strip on the left has a filter rod 22 of the correct length at one end. The next step in the process (not shown in figure 4) is to cut open at the centre of each filter rod 23. The filter element thus obtained is still interconnected on the machine by wrapping it in a continuous envelope 36 with a second filter rod 25, this rod 25 having its envelope paper 31 and having twice the length of the second filter element 24, so as to form an interconnected hidden filter strip, which starts at the left end with a second filter element 24, followed by a first filter element 22, then a cavity 27 with a cavity wall 33 (cavity wall 33 having a cavity 26 in the finished hidden-filter-tipped cigarette 10 and twice the length of the cavity wall 32), followed by the first filter element 22, then the second filter rod 25, and so on. Finally, the hidden filter strip 40, comprising the first filter element 22 made of cellulose acetate and the second filter element 24 made of cellulose acetate plus activated carbon granules, is obtained by cutting this strip in the centre of each second filter rod 25.

Fig. 5 illustrates another method of manufacturing the recessed filter strip 40. Here, in a first step, the cavity wall 33 is glued onto the open communication envelope 36. As can be seen in fig. 5, the distance between the two cavity walls is equal to twice the length of the tobacco-side filter element 24 in the finished recess filter. In a second step of the production method, the filter element 22, here made of cellulose acetate, on the mouth side is glued to the end of the cavity wall 33 by means of the filter sleeve 28. The filter rod 25, here made of cellulose acetate plus activated carbon particles, including its enveloping paper 31, is glued to the communicating envelope 36 between each two cavity wall ends, and this continuous strip is then closed in the next step. In a final step, a cut is still carried out in the centre of each second filter rod 25, thus obtaining a hidden filter strip 40.

Figure 6 shows the production of the final cigarette product from the hidden filter strip 40. The hidden filter strip 40 is first cut in the centre of the filter rod 25, whereby two shorter products are obtained. They each consist of two recess filters which are joined together on their mouth side, i.e. on the outside a second filter element 24 on the tobacco side, followed by a first filter element 22 on the mouth side, and in the center a cavity 27 which is twice as long as the finished hollow cavity 26. Here, the first filter element 22 and the cavity 27 are surrounded by a cavity wall 33 and the entire product is surrounded by a communicating envelope 36. In the final step of the method, the product is now joined, i.e. glued, to the tobacco column 12 by means of a paper wrapper 16, the paper wrapper 16, as is usual, completely surrounding the filter and surrounding the starting region of the tobacco column. If the product thus obtained is now cut centrally, a finished recess-filter cigarette is produced which is similar to recess-filter cigarette 10 shown in figure 3.

Examples 1 to 4

In one of the above-described methods, a recess filter 20, which is specified in table 1 and comprises two filter elements 22, 24, and a cigarette 10 produced therewith are obtained, wherein the cavity wall 32 surrounds the cavity 26 and the mouth-side filter element 22, but not the tobacco-side filter element 24. The cavity wall 32 is made of paper having the following characteristics. Weight per unit area: 110g/m²(ii) a Thickness: 124 μm; permeability: 0Coresta units; tensile strength: 145N/15 mm; the components: strong paper pulp about 87.5%, inorganic filler about 5%, starch slurry about 0.5%, and waterAbout 7%. The mouth-side or cavity-side filter 22 (filter 1) is made of cellulose acetate, and the tobacco-side filter 24 (filter 2) is made of cellulose acetate plus activated carbon particles.

TABLE 1

	Example 1	Example 2	Example 3	Example 4
					Permeability of envelope with filter total length (mm) connectivity1Length (mm) tensile strength of Filter 1 Length (mm) of Cavity Length (mm)2Filter sleeve permeable filter member 2 length (mm) tensile strength2Permeability of filter sleeve1Permeability of cigarette paper and tobacco mixture1Permeability of face paper1(Pre-perforated by laser) tensile Strength of face paper Length (mm) cigarette Length (mm) diameter (mm) cigarette2Air permeability (average,%) tobacco weight (mg) condensate (mg/cigarette) suction section (Zuganzahl)	2712000CU5738 air-proof 154312000CU U.S. mixture 34CU210CU32847.91152067310.97.6	2712000CU5738 air-proof 154312000CU U.S. mixture 34CU700CU32847.991446667.98.2	2712000CU5738 air-proof 154312000CU U.S. mixture 34CU1650CU32847.978606775.48.7	2712000CU5738 air-proof 154312000CU U.S. mixture 34CU1650CU32847.988726662.09.4

In the table, the superscript is 1-in Coresta Units (CU) and 2-in mm water.

These examples show that with the recess filter 20 according to the invention, a total condensation range of 10mg to 2.0mg of paper can be achieved, while the ventilation is between 20 and 72%. Of course, the aeration can be further improved, so that lower condensate values can be achieved.

Example 5

In this case, a conventional product is compared with the product according to the invention. The conventional product relates to a cigarette having a recess filter corresponding to example 4 above, but wherein the cavity wall 32 surrounds the entire recess filter. Venting is achieved by mechanical perforation of the paper and facing paper making up the cavity wall 32. The cigarette 10 according to the invention corresponds to the product described in examples 1 to 4, i.e. the cigarette 10 likewise has two filter elements 22, 24 corresponding to examples 1 to 3 and the final test for table 3 corresponds to example 4, but with a cavity wall 32 only surrounding the cavity 26 and the mouth-side filter element 22. In both comparative cigarettes, the tobacco and filter material used, the filter length, the total cigarette length and all other parameters were identical.

The permeability of the thin face layer was 720 to 2800Coresta units for the comparative products (Table 2) and 150-1650Coresta units for the cigarettes according to the invention (Table 3). This result is shown in tables 2 and 3.

TABLE 2

Comparison product of the prior art

Face paper permeability (Coresta units)	Average value of air permeability (%)	Coefficient of variation (%)
			7209371227210524642800	303340505355	10.39.711.67.96.86.7

TABLE 3

Cigarette according to the invention

Face paper permeability (Coresta units)	Average value of air permeability (%)	Coefficient of variation (%)
			150210 (see example 1)300340600700 (see example 2)1650 (see example 3)1650 (see example 4)	1620273141446072	6.55.96.65.44.53.63.42.9

This comparison shows that the comparative product with the prior art has only 55% ventilation. Higher ventilation is not possible with the filters used, since further mechanical perforation leads to loss of stability in the filter product and other problems. In contrast, significantly higher aeration rates can be achieved with the product according to the invention. The comparison also shows that, in comparable degrees of ventilation, the coefficient of variation of the product according to the invention is reduced by almost half compared with the product being compared.

Claims (19)

1. A smokeable article (10) comprising:

-a column of tobacco (12) surrounded by cigarette paper (14) and/or one or more sheets of tobacco, and

-a ventilated recess filter (20), wherein the tobacco column (12) and the recess filter (20) are interconnected by an at least partially air-permeable thin face layer (16), and wherein

-the recess filter (20) has one or more filter elements (22, 24) at the tobacco-side end of the recess filter (20), a tubular cavity (26) at the mouth-side end of the recess filter (20), and

the cavity (26) is surrounded by a cavity wall (32),

it is characterized in that:

-the ventilation of the recess filter (20) is at least 10%;

-the cavity wall (32) surrounds only the cavity (26), or does not completely surround the cavity (26) and the filter elements (22, 24);

-the length of the cavity (26) is 10mm or less than 10 mm; and

-the ratio of the length of the cavity (26) to the overall length of the recess filter (20) including the length of the cavity (26) is 0.3 or less than 0.3, and

-the porosity of the cavity wall (32) is 100Coresta units or less and is free of perforations.

2. A smokeable article (10) in accordance with claim 1, wherein: the cavity wall (32) surrounds the cavity (26) and the filter elements (22, 24) in such a way that at least at the tobacco-side end of the recess filter (20), one filter element (22, 24) is at least partially not surrounded by the cavity wall (32).

3. A smokeable article (10) in accordance with claim 1, wherein: each filter element (22, 24) is surrounded by a filter sleeve (28, 30), and at least one of the filter sleeves (28, 30) is at least partially gas-permeable.

4. A smokeable article (10) in accordance with claim 3, wherein: the cavity wall (32) and the filter element (22, 24) with its optionally present filter sleeve (28, 30) are surrounded by an at least partially gas-permeable, continuous envelope (34), which envelope (34) is arranged between the thin-face layer (16) and the cavity wall (32) on the one hand and the filter sleeve (28, 30) or the filter element (22, 24) on the other hand.

5. A smoking article (10) in accordance with any one of claims 1 to 4 wherein: the filter elements (22, 24) are cylindrical or cylindroidal.

6. A smoking article (10) in accordance with any one of claims 1 to 4 wherein: the recess filter (20) has a ventilation of at least 40%.

7. A smoking article (10) in accordance with any one of claims 1 to 4 wherein: the length of the cavity (26) is 6mm or less than 6 mm.

8. A smoking article (10) in accordance with any one of claims 1 to 4 wherein: the length of the cavity (26) is 4 to 6mm and the total length of the recess filter (20) is 20 to 40 mm.

9. A smoking article (10) in accordance with any one of claims 1 to 4 wherein: the diameter of the smokeable article (10) is from 5.0 to 8.4 mm.

10. Recess filter (20) for a smokeable article (10), comprising:

-one or more filters (22, 24) on a first end of the recess filter (20),

-a tubular cavity (26) on the second end of the recess filter (20), and

a cavity wall (32) surrounding the cavity (26),

it is characterized in that:

-the ventilation of the recess filter (20) is at least 10%;

-the cavity wall (32) surrounds only the cavity (26), or not completely the cavity and the filter elements (22, 24);

-the cavity wall (32) and the filter elements (22, 24) are surrounded by an at least partially gas-permeable, communicating envelope (34);

-the length of the cavity (26) is 10mm or less than 10 mm; and

-the ratio of the length of the cavity (26) to the overall length of the recess filter (20) including the length of the cavity (26) is 0.3 or less than 0.3;

-the porosity of the cavity wall (32) is 100Coresta units or less and is free of perforations.

11. The recess filter (20) of claim 10 wherein: the cavity wall (32) surrounds the cavity (26) and the filter elements (22, 24) in such a way that at least at the first end of the recess filter (20) one of the filter elements (22, 24) is at least partially not surrounded by the cavity wall (32).

12. The recess filter (20) of claim 10 wherein: each filter element (22, 24) is surrounded by a filter sleeve (28, 30), and at least one of the filter sleeves (28, 30) is at least partially gas-permeable.

13. A recess filter (20) according to any one of claims 10 to 12, wherein: the filter elements (22, 24) are cylindrical or cylindroidal.

14. A recess filter (20) according to any one of claims 10 to 12, wherein: the recess filter (20) has a ventilation of at least 40%.

15. A recess filter (20) according to any one of claims 10 to 12, wherein: the length of the cavity (26) is 6mm or less than 6 mm.

16. A recess filter (20) according to any one of claims 10 to 12, wherein: the length of the cavity (26) is 4 to 6mm and the total length of the recess filter (20) is 20 to 40 mm.

17. A recess filter (20) according to any one of claims 10 to 12, wherein: the recess filter (20) has a diameter of 5.0 to 8.4 mm.

18. A recess filter rod (40) consisting of a plurality of recess filters (20) according to any one of claims 10 to 17, wherein the end of a recess filter (20) on the mouth side is connected to the end of an adjacent recess filter (20) on the mouth side, and the end of a recess filter (20) on the tobacco side is connected to the end of an adjacent recess filter (20) on the tobacco side.

19. A hidden filter rod (40) as claimed in claim 18 consisting of 2, 4 or 6 hidden filters (20).