FR2508774A1 - CIGARETTE FILTER - Google Patents

Abstract

VENTILATED CIGARETTE FILTER WHICH INITIALLY INCLUDES RELATIVELY LOW PRESSURE DROP CHANNELS 8, 3 AND RELATIVELY HIGH PRESSURE DROP CHANNELS 6, 2 FOR THE PASSAGE OF SMOKE THROUGH THEM, THE ARRANGEMENT BEING AS, IN SERVICE , THE INITIAL PREFERENTIAL PASSAGE OF SMOKE IN THE LANES WITH LOW PRESSURE DROP CAUSES THEIR CLOGGING, SO THAT THE PASSAGE OF THE SMOKE IN THE LANES WITH HIGH PRESSURE DROP AND THE DEGREE OF VENTILATION BY AIR ARE INCREASED. APPLICATION TO THE MANUFACTURE OF FILTER CIGARETTES.

Description

The present invention relates to ventilated filters for cigarettes,

  that is to say filters that allow the use of external air intake to dilute the smoke in the filter

  and / or in the smoker's mouth, and it relates more specifically to

  a filter which initially establishes channels with a relatively low pressure drop as well as relatively high pressure loss paths for the passage of smoke, the arrangement being

  such as, in use, the preferential passage of smoke through the

  mediate the path (s) with low pressure drop causes their blocking, so that the passage of smoke through the path (s) with high pressure drop and the degree of ventilation by air are increased.

  Filters according to the invention contribute to uniform

  bet the smell sensation while the cigarette is smoked

  odor sensation produced by a classically ventilated filter cigarette

  It increases as the cigarette is smoked from a low initial value, often unsatisfactory, to a high, often unacceptable value; for a given overall odor sensation, a filter according to the invention establishes in comparison an increased initial value and a reduced final value, and therefore it

creates a smoother smoke.

  In certain types of filters according to the invention, the or each relatively low pressure-loss channel is transversely provided with a barrier which is initially permeable to the

  smoke but which is blocked by the passage of smoke through it.

  In certain preferred embodiments, said barrier comprises

  carries two layers of an air-permeable material (eg paper), one of which has a high air permeability (e.g. 10 to 100 K, preferably about 20 K) whereas the other has an even higher air permeability (for example

  from 50 to 700 K, preferably about 500 K).

  air meltability used in the present patent application

  will be defined in the following Preferably, the barrier is

  placed so that the high permeability layer is placed on the downstream face of the low permeability layer; it is believed that, in use, the sucked smoke passes through the low permeability layer, so that the particles are percussed against the high permeability layer by producing a progressive closure of the pores of the first layer. establish a gradual and uniform increase in the loss of -2-

  load (PD) from one puff to another (and therefore an increase

  more uniform dilution of air) than can be

otherwise obtained.

  In an embodiment according to the invention, the filter comprises an axially elongated core which is provided on its periphery with at least one passage extending from one end of the core only partially towards the other end of this core. and which is in communication, allowing the flow of smoke, with the core, through a means that can be closed by the passage of unfiltered tobacco smoke through said means can, for example, be a barrier to presenting in the form of a core sleeve (eg an envelope) which separates this core from or from each passage; this core sleeve may, for example, be formed of a material permeable to smoke, establishing an intrinsically low pressure drop and which is rapidly closed by the passage of unfiltered tobacco smoke through

  of it, so that the flow of smoke is more and more

  duced or stopped, or it may be formed from an intrinsic material

  a smoke-impermeable seal which has small perforations

  to obtain the same result; we can also

  to deal with a two-layer barrier of the type mentioned above

  A given passage may comprise a groove in the periphery of the core and / or it may be defined between opposed surfaces of the core and profiled sleeve portions. The core and the sleeve may be contoured to create the at least one passage. In another embodiment, the filter has at least one inner passage extending from one end

  the filter only partly from its other end and

  cation, permitting the flow of smoke, with a filter filtering portion of smoke through a means

  be closed by passing unfiltered tobacco smoke through.

  Said means may, for example, be a barrier layer,

  surrounding the passage and separating it from the rest of the filter, this

  initially having a low pressure drop and being permeable to smoke, but being obstructed by the passage of unfiltered tobacco smoke so that the flow of smoke is reduced or stopped; one can, for example deal with a two-layer barrier of the type previously described In other embodiments, the or each passage is a tube of material impervious to smoke which has, at least at its end placed at the inside the filter, a small inside diameter so as to be closed by the

  passage of unfiltered tobacco smoke through.

  Some preferred filters in accordance with the present invention

  have longitudinally adjacent core sections having relatively high and relatively low pressure losses and which are surrounded by a profiled sleeve between it and the core sections one or more passages extending from one end of the filter only. partly towards the other end, a closable barrier being disposed between the passage (s) and the low pressure drop core section. The barrier may be of a two-layer structure of the type mentioned below, or it can be constituted, on the contrary, by

  a single layer of intrinsically permeable material and / or

  The initial path with low pressure drop is therefore established by the core section with a small pressure drop, by the passage or passages and by said intermediate barrier, whereas the path with high pressure drop is established by the sections of pipe. core

  at low and high pressure drop The strong core section

  charge, for example at a pressure drop of between 200 and

  600 mm of water (for example 300 mm) may be formed of a buffer constituting

  fiber (for example cellulose acetate) or paper.

  The core section with low pressure drop may be constituted by a buffer or a tubular element; such a stamp or element

  low pressure drop can come into contact with the

  high pressure drop core, or it may be spaced longitudinally thereof to define a cavity forming a portion of the core section with low pressure drop The said passage or passages may be in communication, allowing the flow of smoke (through said barrier), with the material of the core section with low pressure drop (when this material is permeable to smoke) and / or with a cavity forming part of the

  core section with low pressure drop.

  The core section with low pressure drop is suitably constituted by a pad of a material known under the trade designation "Transorb" (Registered Trade Mark), ie a dense and compact rod formed of filaments The characteristics of the "Transorb" rods, as well as their manufacturing process (which makes it possible to suppress the initial corrugation of the filaments) have been described in the United Kingdom Patent No. 970 817 less towards its downstream end, and in most cases over its entire length, the periphery of the section with high pressure drop is preferably substantially impervious to smoke -for example, thanks to the provision of an integral skin formed by melting (for example by heating or by solvent), or by the provision of a sheath (which may be a casing Cu a coating, for example a coating of adhesive ensuring the

  bonding the section on said barrier).

  In the present description, an air permeability of

  n K defines an air permeability of N × 1000 ml / minute / 10 cm 2 / mm of pressure water, this value being determined by measurement

  the "p" pressure, expressed in mm of water, generated by a

  1050 ml of air per minute through 10 cm 2 of the sample.

  sample, and performing the calculation from the following equation air permeability = 1050 x 100 p-

  Filters according to the invention can be incorporated into

  In the embodiments mentioned above, the filter comprises a part of the low pressure drop channel which is formed by one or more filter-filtered hoods. several passages starting from one end of the filter, it is this end of the filter which abuts against the tobacco column of the cigarette The tip cape may be formed of a breathable material but it is normally constituted of an impermeable material and she

  is provided with ventilation perforations therethrough; the agence-

  is always made in such a way that the amount of ventilation air

  the amount that is aspirated increases as resistance to vacuum

  Smoke flow through the filter increases as the flow of smoke passes from low-pressure pathways to

  lanes with high pressure drop when the cigarette is smoked

  gradually. During the initial manufacture of filters according to the invention, to feed the stage of production of cigarettes

  filter with an external ventilation envelope (intrinsically

  permeable to air and / or perforated), they can be incorporated into cigarettes either with an annular tip or with a

integral cape cape.

  The invention has been described above with reference to ventilated filters, i.e. filters having an envelope

  ventilation system, which may consist of an end cap as-

  The invention also relates to filter elements intended to be combined with a ventilation envelope to form ventilated filters in accordance with the invention. Such elements, examples of which will be described below, are generally characterized by the fact that they comprise an axially elongate integral or composite core body, which is provided with at least one external passage or an internal passage. extending since

  one end of the body only partially towards the other end

  and means for permitting flow of smoke between said passage (s) and the body, said means being closed by passage of unfiltered tobacco smoke through the members. The elements are usually initially produced in the form of rods. or continuous columns and they are immediately cut into

  finished lengths for further handling and

  ducting of filter cigarettes If appropriate, a ventilation casing may be placed continuously around the element as it is formed and before the cut-off is made.

  finished lengths, but the resulting filters conform to the invention.

  then require another surround (ring tip or vent cap) for incorporation into

  filters; when the elements are produced and cut without

  they are usually made in the form of filters according to the invention by setting up a cap of ventilation nozzle during the production of filter cigarettes.

  manufacture of filter cigarettes, an element or long-term filter

  the double wrapper is disposed in such a manner that a wrapped tobacco rod abuts against either end, a surround is set in place to join the tobacco stems and the intermediate double length filter or element and the assembly result is cut in the middle to produce two filter cigarettes The initially produced continuous filter element or filter is normally cut into units of even multiple lengths (for example, six-fold) for supply to the cigarette manufacturer who then cuts them off. multi-length elements of double length elements for use in the production of filter cigarettes as described above It should be noted that,

  in the case of an individual element or filter in accordance with the

  which is asymmetrical (that is, the two ends of which are different), the elements of multiple lengths and of -6-

  lengths from which the sections are finally formed.

  individual classes are usually symmetrical and include

  identical ends The elements and filters of multi-

  ples (in particular double lengths) which are therefore also

  formed in accordance with the present invention comprise a plurality of unitary elements or filters which are arranged in a

  only one end-to-end part, each of said elements or single filters

  are symmetrically arranged in relation to the or each

  unitary element or filter connected to it.

  Other advantages and characteristics of the invention

  will be highlighted, in the rest of the description, given to

  As a nonlimiting example, with reference to the accompanying drawings in which: Figure 1 is a perspective view of a filter element according to the invention; Fig. 2 is a partial sectional view of a filter and a filter cigarette made in accordance with the invention using the filter element of Fig. 1;

  FIG. 3 is a longitudinal sectional view of a

  garette using a different filter element and a filter according to the invention; Figure 4 is a longitudinal sectional view, taken along the line IV-IV of Figure 5, of a filter cigarette using a third filter element and a third filter according to the invention; Figure 5 is a section taken along the line V-V of Figure 4;

  Figures 6, 7 and 8 are longitudinal section views.

  schematic of three different filters and cigarettes

  forms to the invention, the section of Figure 7 being made along lines VII-VII of Figure 11; Figures 9 and 10 are sectional views of the embodiment of Figure 6 through the area of its inner cavity 63 and its upstream end zone; FIG. 11 is a sectional view of the embodiment of FIG. 7 through its upstream end zone, and FIGS. 12 to 14 are diagrammatic views in longitudinal section of three different length filter elements.

sixfold according to the invention.

  The filter element shown in FIG. 1 comprises a core 2 formed of a bundle of cellulose acetate fibers bonded together, which is wrapped by a buffer surround.

  2 and the buffer surround 3 are partially crimped at one end.

  mite 4 to form a core section 6 of reduced section, surrounded by four grooves or channels 8 arranged symmetrically and separated by ribs or fins 10 The surrounding buffer 3 is formed

  porous paper that offers low initial resistance to

  of smoke, but which is gradually closed off by

  of unfiltered tobacco smoke passing through it.

  be provided with a smooth outer surround made of

  air-permeable and / or perforated, in which case it could be incor-

  pored to a filter cigarette via an annular tip

  lar. The element shown can be produced by continuously producing in a conventional manner a rod of cellulose acetate fibers wrapped by an entourage 3, by folding this rod.

  at intervals and by sectioning the resultant pleated rod trans-

  salty through adjacent pleated and unfolded areas -

  as previously explained, this bucking would be

  edge made in symmetrical multiple lengths, then in symmetrical double lengths and, finally, in asymmetrical single lengths

  The filter element of Figure 1, incorporated in a cigar

  rette, has been shown in Figure 2, which shows that the element (shown in side elevation) abuts by its end 4 against a wrapped tobacco column 12 (shown in section) and is fixed on the tobacco rod by a tip cap 14 formed of an impermeable material and provided with a circumferential ring of ventilation perforations 16 In use, the smoke emerging from the tobacco rod is initially sucked preferentially along the low-loss pathway charge, that is to say along the channels 8 and through the buffer surround 3 towards the unfolded portion of the core 2; the transmission of odor components to the smoker is therefore relatively large and the degree of dilution by air through the perforations

  16 to the core 2 is relatively weak after the first

  puffs (for example three or four),

  However, it is blocked by the passage of the unfiltered smoke through and the smoke coming from the tobacco column is more and more obliged to follow the lane with the greatest pressure drop to reach the reduced section 6 and flow over the entire length

  core 2; the degree of smoke filtering increases accordingly.

  with the degree of ventilation, which tends to counterbalance

  the increase in tars transmission, etc., which is

  Normally, during the last puffs of a conventional filter cigarette, therefore, a given total transmission of tar can be ensured at a more uniform rate of puff.

  the other with a conventional filter.

  It should be noted that although a unitary core 2 has been represented, many variants are possible; thus, the core could be constituted by a composite structure formed of two sections placed end to end having different characteristics

  (for example different pressure drops); another possibility

  it is to provide the buccal end of nucleus 2 with a

internal cavity.

  The filter element according to the invention which has been shown in FIG. 3 comprises a core formed of a smoke filter material and provided with an internal cavity 22 opening at its end 4 and surrounded by a body formed of a bundle of cellulose acetate fibers 24 and giving rise to a loss of

  relatively high load cavity 22 is separated from the body

  Vironnant 24 by a tube 26 which consists of an impermeable material

  Smoke-resistant and decreasing in section inside the filter

  up to a constricted orifice 28; the body 24 and the exit of the ori-

  FIG. 28 abuts against a buffer 38 formed of a bundle of cellulose acetate fibers and with relatively low pressure drop, the body 24 and the buffer 30 being joined by a porous peripheral surround 32. The filter according to the invention consists of this filter element and the peripheral tip cap 14 by means of which it is fixed by the end 4 on a wrapped tobacco rod 12; the end cap 14 is provided with a ring

  circumferential ventilation perforations 16.

  The initial way of passing smoke with a weak

  pressure loss is in this case constituted by the cavity 22 and the ori-

  fice 28 opening into the buffer 30, the transmission of tars

  therefore relatively large and the ventilation

  to perforations 16 relatively weak After a few bouf-

  the orifice 28 is closed by the passage of unfiltered smoke, an increasing amount of smoke must therefore pass through the body 24 with high pressure drop to reach the buffer 30, which increases the effectiveness of filtering and degree

ventilation, as before.

  The filter element according to the invention shown in FIGS. 4 and 5 comprises a core 2 formed of an element with a high pressure drop 40 and a low-pressure loss element 42, which are maintained. assembled around a surround of buffer 3 Around surrounding 3, there is provided another envelope 44 formed of a material impervious to smoke and air and which is provided with

  respective rows of longitudinally extending corrugations 46, -

  48 at the ends 4 and 50 of the element, these undulations being separated

  The corrugations 46 define, with the core 2, longitudinal channels 54 which extend from the circumferential corrugations 52.

  end 4 and ending in the circumferential

  52, while the undulations 48 define, on the outside

  of the element, the longitudinal channels 56 which extend from the corrugated

  circumferential movements 52 to the end 50 of the element.

  The buffer surround 3 is formed of a smoke impervious material and has perforations 55 at the inner ends.

  the channels 54 around the buffer 42 The perforations 55 are pro-

  grésively blocked by the smoke passing through them.

  In the filter shown, the filter element is provided with a ventilation envelope 14 which constitutes a cape connecting the element to the wrapped tobacco rod 12 at its end 4 The ventilation perforations 16 formed in the cloak The initial low pressure drop channel for the smoke is located in this case along the grooves 54, through the part of the buffer surround 3 located at the ends. said grooves where it surrounds the core member 42 with low pressure drop, then through the latter to the mouth end 50; as for the other embodiments, the initial transmission of tar

  is quite high, while the degree of dilution by air (direc-

  in the smoker's mouth via the passages 56)

  is relatively weak After the first puffs, the perforations

  55 through which the unfiltered smoke has passed to arrive in the low pressure drop element 42 are obstructed,

  and a growing amount of smoke is forced to pass through

  milking in the element 42 through the core element with high pressure drop, which results in an increase in the filtering effect and the degree of ventilation The walls of the corrugations 48 could be perforated that ventilation air entering the channels 56 from perforations -10-

  16 can also pass into the adjacent channels 57 formed

  The undulations and the surrounding buffer 3 before being sucked into the smoker's mouth The walls of the corrugations 46 could be perforated in the same way to allow a passage of smoke (during the first puffs) in all the channels (54). and 53) formed between the end cap 14, the undulations 46 and the buffer surround 3. It is evident that the casing 44 could be formed

  of a material having a certain degree of intrinsic permeability.

  A cut made through the end with the

  ripples 46 has an appearance similar to FIG. 5 without the perforations

rations 16.

  The buffer surround 3 comprising the perforations 55 and shown in FIGS. 4 and 5 could be replaced by an inherently permeable and closable buffer surround 3 of the type described with reference to FIGS. 1 and 2, and in particular by an entourage formed of two layers of paper in which the

  outer layer (upstream) would have an air permeability of

  20 K and the inner layer (downstream) an air permeability of about 500 K. Similarly, the tube 26 provided with the orifice 28 and shown in FIG. 3 could be replaced by a tube such as that of FIG. 1 or such that the abovementioned two-layer buffer surround, closed at its downstream end, for example by being pleated in the manner indicated for the end 4 in FIG.

  completely closing the end.

  FIGS. 6, 9 and 10 show a filter comprising a core section 42 of small pressure drop which is formed by a tubular element 61 and which comprises a cavity 63 through which

  the tubular element is longitudinally spaced from a

  the pressure drop 40 consisting of a smoke filtering material

  The tubular element 61 may be formed of a fine material

  fibrous or non-fibrous, permeable or impervious to smoke

  buffer 40 is suitably a filament bundle

  groupings (eg of cellulose acetate) or of

  pier, its pressure loss being about 300 mm of water A sleeve 3, surrounding the core parts and ensuring their joining, constitutes the barrier which is initially permeable to smoke but which is progressively obstructed by the smoke passing through it. sleeve 3

  is appropriately constituted by an envelope which is

  tagged glued on the elements 62 and 40 The sleeve 3 is

  in this case a two-layer paper envelope, of which the inner layer (upstream) has a permeability of 20 K and the outer layer (of downstream) a permeability of 500 K The sleeve 3 could however to be formed in another way and avoiz

  another structure provided that the described function is fulfilled.

  Immediately around the sleeve 3 forming a barrier, it is

  provided a profiled sleeve 44 which is for example longitudinally corrugated

  The internal and external grooves 66, 68 formed by the sleeve 44 open out at the end 50 of the filter around the surface of the filter and can be air permeable (but which is not permeable in this case). buffer 40 and extend in its longitudinal direction only over a portion of the length of the filter, terminating in an area 67 around the core segment with low pressure drop; in the zone 67, the sleeve 44 can simply be left smooth and non-profiled, a filling part 80 (formed for example of a thermoplastic material) compensating for the difference in outside diameter and closing off passages which would lead to

  otherwise at this end of the tube Internal grooves 66 may

  wind for example have a depth between 0.5 and 1 mm and have a pitch of about 1 mm in the case of a dimension filter

  conventional, approximately 23 uniformly distributed grooves

  In use, the filter may be attached to a wrapped tobacco rod 12, as shown, with a vent cap wrapper 14, which may be formed

  intrinsically permeable to air and / or perforated

  ventilation (as indicated in 16) leading to

  In use, tobacco smoke flows, during a puff, from the tobacco rod 12 through the tubular element 61. During the initial puffs, at least the majority of the smoke passes through the 3 forming a barrier to penetrate the internal passages 66 formed between the sleeves 3 and 44 and then to reach the smoker's mouth, which

  corresponds to the path of minimum pressure drop.

  The collapse of smoke arriving on the inner face of the sleeve 3 passes through the porous paper with a porosity of 20 K and the particles tend to abut against the porous paper

  500 K, thus producing a gradual filling of the pores.

  As a result, the transfer of the smoke flow from this initial channel to that corresponding to the high loss element

  charge 40 occurs uniformly and progressively in

  an increase in the pressure drop puffed by puff.

-12 2508774

  When this gradual increase in the loss of

  puff load per puff occurs, there is an increase in

  gradual flow of ventilation air flow through

  the end cape 14 This air flow arrives in the passages

  68 and then into the smoker's mouth.

  Figures 7 and 11 represent another embodiment of

  in which spaced apart segments 61 and 40 are similar to

  those highlighted in Figure 6 and are wrapped as aupa-

  a sleeve 3 consisting of two air-permeable and barrier layers (the completely inner layer having a permeability of 500 K). A longitudinally corrugated sleeve 44 envelops the assembly, a circumferential groove 77 closing the openings.

  passages 66 but not passages 68 which are closed off by a

  Thermoplastic 80 in zone 67.

  In use, the flow of smoke predominates, in the initial puffs, in the internal passages 66, the flow path being derived in the interruption zones 77 and then passing through the low-loss envelope.

  initial charge 3 to then reach the smoker's mouth.

  When the casing 3 is gradually closed off by smoke particles, its pressure loss gradually increases and the smoke is uniformly diverted towards the high loss segment.

charge 40.

  As in the embodiment of Figure 6, there occurs in each successive puff a progressive and uniform increase in the pressure drop and ventilation in the filter. FIG. 8 represents yet another embodiment in which a core section 42 and a second core section 40

  are placed axially end to end The section 42 is a cymbal body

  lindrique formed of a porous material (e.g.

  cellulose) and having a very low pressure drop -

  preferably about 15 mm of water The section 40 is a body

  cylindrical porous material (formed for example

  cellulose) and having a high pressure drop, of pre-

  300 mm of water The sections 40 and 42 are

  equipped with a sleeve 3 forming a barrier and arranged in the same way as in FIG. 6 The envelope 3 can be fixed on the section 40 around its periphery The assembly 40 is wrapped with a longitudinally corrugated material 44, the passages 66 and 68 ending in an upstream zone 67 as in FIG. 6 A tobacco rod or column 12 is attached to the filter assembly with a cape

  made of perforated paper (as in 16) or permeable paper 14.

  As indicated by the arrows highlighting the

  While the smoke is running, the operation of the filter while a cigar is being smoked is similar to that described for Figure 6. The initial flow of smoke passes through the material of the buffer 42 and through the barrier 3 to get into the passages 66, but it is drifting gradually towards the passing way

  through buffers 40 and 42, with increased ventilation

  through passages 68.

  It is possible to make various modifications to the embodiments shown. For example, in the embodiments of FIGS. 6, 9, 10 and in that of FIG.

  corrugated sleeve 44 may be permeable to smoke or air,

  trinsically and / or through perforations; of the

  smoke and air can therefore be mixed in

  wise 66, 68 until the flow of smoke through the barrier 3 and to the passages 66 ceases during the closure of this barrier 3; in these variants, while a cigarette

  is smoked, both passages 66 and 68 are available for a

  ventilation air, which can therefore be increased by comparison with the case where the air flow can pass only

by external passages.

  In the embodiments shown in the figures

  4 to 11, the core section 40 with high pressure drop can

  a circumferential surface which is made impervious to smoke by an adhesive coating by means of which it is fixed on

  the barrier sleeve 3, but the necessary degree of impermeability

  The extent, and extent, of the area of the high pressure drop section 40 can be established in other ways, as previously indicated. As explained above, a filter element or a filter according to the invention, such as any one of

  those shown, is initially realized in the form of a long

  continuous pattern in which rods of even multiple lengths are cut (i.e., each rod is an even multiple of the final individual element or filter), the rods of multiple lengths being further subdivided into length elements double, Then, during the production of filter cigarettes, in -14-

  final elements of simple length Examples of long stems

  The sextuple lengths according to the invention, which can be further subdivided into individual elements according to the invention, have been shown diagrammatically in FIGS. 12 to 14. FIG. 12 represents a six-fold length shaft from which elements and filters of simple length, such as those of

  Figures 1 and 2 can be produced by first carrying out a

  halfway cutting the longitudinally grooved portions in the positions 82 to produce double length rods, the sectioning being then performed, during the manufacture of the filter cigarettes, as described above, in positions 84; six-fold length rod that can be cut in a similar manner first at 82 mid-distance

* through the inner tubular elements 61, then 84 to 50

  distance through the elements with high pressure drop 40 in order to

  produce individual elements, filters and ciga-

  filter retorts of the type shown in Figure 6; FIG. 14 represents a shaft of six-fold length which can be cut in the same way at 82 through internal low-pressure-drop elements 42, then at 84 through elements with high pressure drop 40 in order to form individual elements, filters and filter cigarettes of the type indicated in FIG. 8 In FIGS. 13 and 14, the tip made of thermoplastic material of the final products has not been shown, this endpiece 80

  could be set up locally in the corresponding areas

  in a partial operation involved in the continuous manufacture of the rod; it could also be implemented on the multi-length stem sections, or on the double length or single length rod sections, before, during or after the incorporation of said sections to filter cigarettes. 12 to 14, we realize

  conveniently of the shape of the rods of multiple lengths which

  come to manufacture other types of filter elements, filters and filter cigarettes according to the invention (for

  example those of Figures 3 to 5, 7 and 11).

  Stems of multiple lengths may be provided with an air permeable buffer surround that would normally be continuously positioned on the stem initially produced prior to cutting in multiple lengths; tip 80 should

  then be put in place on the initial continuous element before

-15 2508774

  The resulting filters could be fixed on

  cigarettes by ring tips or by caps of

end of ventilation.

  It should be noted that, to clarify the representation, the drawings are not to scale, at least in large part; As a result, the radial depth of the undulations 46 and 48 of FIGS. 4 and 5 is well exaggerated and their number and the core diameter are correspondingly reduced.

  all embodiments using a corrugated sleeve 44,

  the entire diameter (approximately 8 mm) of the

  filter or filter according to the invention is usually used.

  by the core, the corrugations having a radial depth which is for example about 0.25 to 1 mm, for example 0.5 mm, as shown in Figure 11 Where there is shown a single ventilation perforation 16 for each external passage (56 or 58), the perforations may be more closely spaced,

  two or more corrugations communicating with each of said passages.

  Although Figures 4 to 11 use an imperforate envelope

  For example, the impermeable envelope could be formed of thick paper (eg 100 g / m 2 or more), such as cartridge paper having channels 54, 56 (or 66, 68) formed by longitudinal grooves formed

  in the paper, advantageously using profiled rollers of

  preinte; the surfaces of the paper could be left smooth

  in the areas where the passages formed by the

  develops. When the filtering core of a filter or filter element according to the invention consists of a composite set of two or more core elements, one or some of the core elements should not exert a filtering effect but simply For example, in FIGS. 4 to 11, the buffer 40 could be replaced by a buffer which does not exert a filtering effect and which has peripheral and / or internal channels for the essentially unfiltered smoke passage in front of it. and / or through said buffer, but producing a loss of head

  In such cases, the increase in ventila-

  when transferring smoke from low pressure loss pathways to high pressure loss paths may be accompanied by

  a small or no increase in the filtration effect.

  When a filter according to the invention comprises core sections with low and high pressure drop, the inlet of the ventilation air, as in the embodiments of FIGS. 4 and 6 to 8 (by example the position of the ventilation perforations in the outer casing of the film), is often preferably located mainly or only around the section with high pressure drop.

  In filters and filter elements in accordance with the

  vention, there may be a recess in the mouth-end -

  thus, in the embodiment of Figure 4, the core 2 may terminate a short distance from the end 50, for example at a short distance from the corrugations 48, so that the ventilation passages 56 do not overlap longitudinally with the

core 2.

  It has been stated above that wire elements and rods

  according to the invention and with multiple lengths can

  include several elements or unit filters in accordance with the

  which are arranged jointly end to end, each element

  unitary filter being placed symmetrically with respect to the or each adjacent unitary element or filter. In the case of the multi-length embodiments which have been shown

  Figures 13 and 14 (and by comparison with the long-term

  unit of FIGS. 6 and 8), for example, one realizes

  however, these elements do not include the part of

  which is a necessary part of the long-term

  at least one unit when incorporated in filter cigarettes. The invention therefore also relates to

  elements and filters of multiple (and unitary) lengths in the ab-

  the presence of such a filling part 80 or of a part

  may be necessary in the filter cigarette to ensure the necessary increase in air dilution with switching of smoke flow from low

  loss of load to high pressure loss paths.

  The filling part 80, when it must intervene

  as a multi-length stem part, could for example

  can be placed locally on the barrier 3 by printing before this barrier is wrapped around the core during the initial production of the continuous rod; a permeable envelope could, if necessary, be put in place around the element of

  resulting composite core and the surrounding barrier (preferably

-17 2508774

  before the cutting of the rod produced continuously in

  sections of multiple lengths) in order to protect the

  pleating 80 during subsequent handling operations at

  perform before and during the production of filter cigarettes.

  In embodiments of the type involving

  a profiled sleeve 44 providing longitudinal passages

  which must end in the same place, the steps

  wise, can be terminated by a circumferential

  For example, in FIGS. 6 and 8, the portion of the sleeve

  smooth of the envelope 44 and the filling 80 could be replaced

  placed by one or more circumferential corrugations in the casing 44, as indicated at 52 in Figure 4; in FIGS. 13 and 14, the smooth parts placed around the tubular elements 61 (FIG. 13) and the buffers 42 (FIG. 14) could then be replaced by circumferentially corrugated portions.

  Although we have involved in the description given

  above a barrier that can be closed by the passage of

  unfiltered, it goes without saying that the invention is not limited to

  cases where the smoke in practice reaches the barrier in a

  totally unfiltered edition Thus, the tobacco itself acts

  always like a filter; in Figure 8, it necessarily occurs

  42, while in other embodiments, the smoke passes directly from the tobacco.

  in the barrier and a certain amount of conden-

  constituents of smoke upstream of the barrier; it is then obvious that a filter material could be placed in this part of the path, for example in the passages 66. It is nevertheless preferable to keep the effect of

  filtering occurring between the tobacco and the barrier because, other-

  the barrier blocking effect could be reduced too much

  strongly to gain a significant advantage.

-18-

Claims (11)

  1 Ventilated filter for cigarettes, characterized in that it initially comprises relatively low pressure loss paths (8, 3, 2) and relatively high pressure loss paths for the passage of smoke through said channels, arrangement being such that, in use, the initial preferential passage of the smoke in the low pressure drop channel (s) produces their closure so that the passage of the smoke in the path (es) with high pressure drop and the degree air ventilation are increased.   2 Filter according to Claim 1, characterized in that a barrier (13) which is initially permeable to smoke but which is closed off by the passage of smoke at the outlet side is provided transversely to the or each path with a relatively low pressure drop. through her.   3 Filter according to claim 2, characterized in that the barrier consists of two layers of an air permeable material of which one layer has an air permeability of 10 to 100 K, while the other layer has air permeability superior to the first.   4 filter according to claim 3, characterized in that the layer of high permeability is located on the downstream face of the low permeability layer.   Filter according to any one of claims 1 to 4,   characterized in that it comprises an axially elongated core (2),   provided on its periphery with at least one passage extending from   the end of the core only partially towards the other end and which is in communication, allowing a flow of smoke, with the core via a means that can be closed by the   passage of tobacco smoke through him.   6 Filter according to claim 5, characterized in that said means is a barrier in the form of a   sleeve separating the core from or from each passage.   Filter according to any one of claims 1 to 4,   characterized in that it comprises at least one internal passage extending   from one end of the filter only partially to the other end and in communication, allowing a flow of _   smoke, with a portion of filter smoke filtering through the   a means that can be closed by the passage of smoke from tobacco through him. -19 2508774   Filter according to claim 7, characterized in that said means is a barrier layer, surrounding the passage and separating it from the rest of the filter.   9 Filter according to claim 7, characterized in that the or each passage is a tube of material impervious to smoke which, at least at its end placed inside the filter, has an inside diameter sufficiently small to be closed by the   passage of tobacco smoke through him.   Filter according to any one of claims 1 to   6, characterized in that it comprises longitudinally adjacent core sections, having relatively high and relatively low charge losses and surrounded by a profiled sleeve leaving between itself and the core sections one or more passages s' extending from one end of the filter only partially towards the other end, and in that there is provided between the passage (s) and the core section with a low pressure drop a barrier which is initially permeable to smoke but which is closed off   gradually through the passage of tobacco smoke through it.   11 Cigarette filter element, characterized in that   comprises a filter according to any one of claims 1 to 10,   without external ventilation envelope.   Filter cigarette, characterized in that it comprises a filter or a filter element in accordance with any one of   1 to 11, which is incorporated in it by an end cap ventilation.   Filter or filter element for tobacco smoke, characterized in that it is of multiple length and comprises several: filters or unit filter elements in accordance with any one of:   claims 1 to 11, which are arranged integrally end to   end, each element or unit filter being placed symmetrically with respect to the or each element or unitary filter integrally adjacent.