FR2508773A1 - DEVICE FOR FILTRATION OF TOBACCO SMOKE - Google Patents

Abstract

THE INVENTION RELATES TO A TOBACCO SMOKE FILTERING DEVICE WHICH INCLUDES CHANNELS INITIALLY HAVING RELATIVELY LOW PRESSURE DROPS 8, 3 AND CHANNELS INITIALLY HAVING RELATIVELY LARGE PRESSURE DROPS 6, 2 TO ALLOW THE PASSAGE OF THE SMOKE, THE OR EACH LANE HAS A RELATIVELY LOW PRESSURE DROP BEING TRANSVERSALLY PROVIDED WITH A BARRIER WHICH IS INITIALLY PERMEABLE TO SMOKE AND WHICH IS SUBSEQUENTLY OBSTRUCTED BY THE PASSAGE OF THE SMOKE THROUGH IT SO THAT, WHEN THE CIGARETTE IS PRE-SMOKE, THE PASSAGE SMOKE IN THE LOW PRESSURE DROP LANE (S) CAUSES THEIR OBSTRUCTION SO THAT THE PASSAGE OF SMOKE IN THE HIGH PRESSURE DROP LANE (S) IS INCREASED. APPLICATION TO THE MANUFACTURE OF CIGARETTES.

Description

The present invention relates to tobacco smoke filters and

  it relates to a filter which initially establishes relatively low pressure drop channels and relatively high pressure loss paths for the passage of smoke, the or each relatively low pressure loss path being provided transversely with a barrier which is initially permeable to smoke but is blocked by the passage of smoke passing through it so that,

  in service, the initial preferential passage of smoke through the

  The low pressure drop channel (s) produces their shutter so that the passage of the smoke in the channel (s).

  with high pressure drop is increased.

  Filters according to the invention contribute to uniform

  bet the taste transmission while a cigarette is smoked The taste transmission of a conventional filter cigarette increases as this cigarette is smoked from an initial value

  weak and often unsatisfactory to a high value and often

  unacceptable wind; for a given total transmission of taste, a filter according to the invention establishes by comparison an increased initial value and a reduced final value and consequently a

more uniform smoke.

  In certain preferred embodiments, said bar

  comprises two layers of a sheet of breathable material (for example paper), one of which has a high air permeability (for example between 10 and 100 K),

  preferably about 20 K) and the other an air permeability of

  higher core (eg from 50 to 700 K, preferably from

  500 K) The units of air permeability used in the

  present description will be defined in the following Preferably

  the barrier is arranged so that the layer of large permeation

  on the downstream face of the low

  méabilité; it is believed that, in use, the aspirated smoke passes through the low permeability layer so that the particles tend to abut the high permeability layer by producing progressive pore sealing.

  of the first layer This arrangement makes it possible to create an increase

  gradual and uniform pressure drop (PD), and consequently a more uniform transfer of smoke flow from low pressure loss pathways to high loss pathways.

  load compared to what could be obtained otherwise.

  In one 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 may, for example, be a barrier in the form of a core sleeve (for example an envelope) which separates this core from the or each passage; this core sleeve can,

  for example, be made of a material permeable to smoke, established

  an inherently low pressure drop which is rapidly

  blocked 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 internal passage extending from one end of the

  filter only partly from its other end and in communi-

  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 layer initially having a low pressure drop and being permeable to smoke, but being obstructed by the passage of tobacco smoke -non-filtered so that the smoke flow is more and more reduced or stopped; we can, for example, have to deal with a barrier

  two-layer of the type previously described.

  Some preferred filters in accordance with the present invention

  There are longitudinally adjacent core sections having relatively high and relatively low pressure losses and which are surrounded by a profiled sleeve between them and the core sections one or more passages extending from one end. the filter only partially towards the other end, a closable barrier being disposed between the passages and the core section with low pressure drop 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 an intrinsically permeable and / or perforated material. The initial low-pressure loss path is therefore established E by the core section with a small pressure drop, by the passage or passages and by said intermediate barrier, while the high pressure loss path is established by the weak core sections E and strong pert The core section with a high pressure drop, for example with a pressure drop of between 200 and 600 mm of water (for example 300 mm), can be formed of a buffer made of fibers (for example acetate fibers). cellulose) or paper The core section with low pressure drop can be constituted by a buffer or a tubular element; such a buffer or tubular member with low pressure drop can abut against the core section with high pressure drop, or it can be spaced longitudinally thereof to define a cavity forming a part of the low core section loss of charge The passage or passages may

  to be in communication, allowing the flow of smoke (through

  intermediate of 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 at

low pressure drop.

  The core section with low pressure drop is suitably constituted by a pad of a material known under the trade designation of "Transorb" (Registered Trade Mark), that is to say

  a dense and compact stem made of cellulose acetate filaments

  linked together The characteristics of the "Transorb" stems, as well as

  manufacturing process (which eliminates

  initial filamentation) have been described in UK Patent No. 970,817. At least towards its downstream end, and in most cases throughout its length, the periphery of the high pressure loss section is preferably essentially impermeable. to the smoke -for example by the provision of integral skin formed by fusion (for example by heating or by solvent>, or by the provision of a sheath (which may be an envelope or a coating, for example a adhesive coating ensuring -4-

  bonding the section on said barrier).

  In the present description, an air permeability of

  * n K defines an air permeability of N x 1000 ml / minute / 10 cm / mm of pressure water this value being determined by measuring the pressure "p", expressed in mm of water, generated by a DISCHARGE

  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, where the filter comprises a portion of the low-pressure path which is formed by one or more of the filter-type hoods in a conventional manner. 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 filter cigarettes production stage with an outer ventilation envelope (intrinsically permeable to air and / or perforated), they can be incorporated into the cigarettes either using an annular tip, or using a

integral cape cape.

  Some filters according to the invention require a

  predetermined outer envelope, for example for the purpose of

  complete installation of the low-pressure pathway (s)

  The present invention also relates to the filter elements

  which are intended to be combined with an outer envelope

  to produce filters according to the invention.

  Such elements, examples of which will be described below, are generally characterized by the fact that they comprise an axially elongated integral or composite core body, which is

  provided with at least one external passage or an internal passage extending

  from one end of the body only partially towards the other end, and a means for allowing a flow of smoke between the aforementioned passage (s) and the body, said means being closed by the passage of unfiltered tobacco smoke to the The elements are usually initially produced in the form of continuous rods or columns and 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 element or continuous filter initially produced is normally cut into units of even multiple lengths (eg, six-fold) for

  supply to the cigarette manufacturer who then provides the

  These multi-length elements are formed into 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 invention. , who

  is asymmetric (that is, both ends of which are

  rents), the elements of multiple lengths and double lengths from which the individual sections are finally formed are usually symmetrical and have identical ends. The elements and filters of multiple lengths (especially of double lengths) which are therefore also formed, in accordance with the present invention comprises a plurality of unitary elements or filters which are arranged in one piece end to end, each of said unitary elements or filters being arranged symmetrically with respect to the or each unitary element or filter which is connected thereto. 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 schematic longitudinal sectional views of three different filters and cigarettes according to the invention, the section of Figure 7 being taken 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 enveloped by a surrounding buffer 3. The core 2 and the buffer surround 3 are partially crimped at one end 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 buffer surround 3 is formed of a porous paper that offers resistance initially weak at the passage of the smoke, but which is progressively closed off by the flow of unfiltered tobacco smoke passing through it. The element could be provided with a smooth outer surround formed of an air-permeable material and / or perforated in which case, it could be incorporated in a filter cigarette via an annular tip. 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 O

  intervals and sectioning the resultant folded shank

  salty through adjacent pleated and unfolded areas -

  as previously explained, this bucking would be

  edge made in symmetrical multiple lengths, then in lengths

  symmetrical doubles and finally in asymmetric simple lengths

c.

  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

  in core 2 is relatively weak After the first bouts

  fairy (for example three or four), the surrounding buffer, 3 is however closed by the passage of unfiltered smoke through and the smoke from the tobacco column is more and more obliged to follow the path to more high pressure drop to reach the reduced section 6 and flow over the entire length of the core 2; the degree of smoke filtering therefore increases with ventilation, which tends to counterbalance the increase in tar transmission, etc., which normally occurs

  during the last puffs of a classic filter cigarette.

  As a result, a given total transmission of tar can be ensured at a more uniform flow rate from one puff to the other than with a

classic filter.

  It should be noted that, although a unitary core 2 has been represented, numerous variants are possible; thus, the core could be constituted by a composite structure formed of two end-to-end sections having different characteristics (for example different pressure drops); another possibility is to provide the buccal end of the nucleus 2 with a

internal cavity.

  The embodiment of the filter according to the invention which has been shown in FIG. 3 comprises a body 20 formed of a smoke filtering material, for example a bundle of bound cellulose acetate fibers, which comprises a surrounding of buffer

  32 and an internal cavity 22 open to its ex-

  The cavity 22 is separated from the surrounding body 20 by a tubular wall 26 (formed of the same material as the surrounding area

  of buffer 3 of FIGS. 1 and 2), which decreases from section to

  The filter according to the invention is attached by its end 4 to a tobacco rod.

  wrapped 12 by a cape cap 14.

  The initial passage of the smoke with low pressure drop is established in this case via the cavity 22

  and the wall 26 into the body 20, the transmission of gou-

  Drons being thus relatively large After a few puffs, the wall 26 is closed under the effect of the passage of unfiltered smoke through, an increasing amount of smoke passing through

  therefore the entire length of the body 20 from its end of a-

  mount 4 so that filtering efficiency increases as aupa-

  The end 28 is pleated in the general manner indicated in FIG. 1, except that the pleating completely closes the tube of material 3, the ribs 10 extending inwards to

in the filling zone 28.

  The filter of FIGS. 4 and 5 according to the invention

  carries a core 2 formed of a member 40 with a large pressure drop and a low-pressure drop element 42, these elements 40, 42 being

  held together by an entourage of buffer 3 Around the

  3, there is provided another envelope 44 formed of a material impervious to smoke and air, which comprises corrugations 46 oriented longitudinally and starting from the end 4 to

  end at circumferential corrugations 52 existing at the end

  The corrugations 46 define with the core 2 longitudinal channels 54 which start from the end 4 and end at the circumferential corrugations 52 The buffer surround 3 is of the type described above with reference to FIGS. 1 and 2.

  filter comprises an envelope 14 which is an end cap

  The initial path of passage of the smoke with low pressure drop is established in this case along the grooves 54, through the part of the entourage 3. placed at the ends of said grooves, where it surrounds the core member 42 with low pressure drop, then through this element to the end

  oral 50; as for the other embodiments, the trans-

  Initial tar mission is therefore quite large After the first puffs, the buffer surround 3 through which the unfiltered smoke has passed to enter the low-pressure element 42 is closed and an increasing amount of smoke

  obliged to switch to element 42

  The core walls 40 of the corrugations 46 may be perforated or have a certain degree of intrinsic permeability in order to allow passage of the smoke ( during the first puffs) in all the channels (54 and 53) formed between the tip cap 14, the undulations 46

and the surrounding buffer 3.

  The buffer surround 3 could be replaced by an entourage with small perforations that initially pass the smoke but are then closed, or it could be replaced by a two-layer envelope as

previously described.

  Similarly, the tube 26 of FIG. 3 could be replaced by a tube of the type of the two-layer buffer surround described

  above (the layer placed inside having the greatest

  meability), this environment being folded so as to be closed to

its downstream end.

  The filters of FIGS. 6 to 11 comprise an outer ventilation envelope, the transfer of the smoke flow from the low pressure loss pathways to the high loss pathways.

  charge being accompanied in this case by an increase in the

  ventilation air passing through this envelope and penetrating into the smoker's mouth In each case, the envelope

  could be replaced by an envelope

  not wrinkling a ventilation effect.

  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 has a cavity 63 through which the tubular element is longitudinally spaced from a High pressure drop buffer 40 made of a tobacco smoke filtering material The tubular element 61 may be formed of a fibrous or non-fibrous material, permeable or impervious to smoke. The pad 40 is suitably a bundle of bundled filaments (for example cellulose acetate) or paper, its pressure drop 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 is obstructed

  gradually through the smoke passing through it The sleeve 3 is con-

  suitably stuck by an envelope which is advantageously adhered to the elements 62 and 40 The sleeve 3 is constituted in this case by a two-layer paper envelope, the layer of which

  (upstream) has a permeability of 20 K and the outer layer

  (downstream) a permeability of 500 K The sleeve 3 could

  however be formed in another way and have another structure

  provided that the function described is fulfilled.

  Immediately around the sleeve 3 forming a barrier, it is

  provided a profiled sleeve 44 which is for example longitudinally corrugated

  paper and which can be breathable (but

  which is not in this case) Internal and external grooves-66, -

  68 formed by the sleeve 44 open at the end 50 of the filter around the pad 40 and extend in its longitudinal direction only over a portion of the length of the filter, ending in an area 67 located around the core portion to low pressure loss; 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

-11-

  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 flow 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.

  When this gradual increase in the loss of

  puff load per puff occurs, there is an increase in

  progressive flow of the ventilation air flow through the end cap 14 This flow of air arrives in the passages

  outside 68 and then into the smoker's mouth.

  Figures 7 and 11 show another embodiment 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. charge

  initial 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 FIG. 6, there is produced at each successive puff a gradual increase and

  uniform pressure drop and ventilation in the filter.

  In variants, it is not planned to dilute the air through the cape 14 and in this case the two passages 66 and 68 are terminated at 77 (for example with the aid of a material insert). thermoplastic) and the

filling 80.

  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 cylindrical body

  of porous material (formed for example of cellulose acetate fibers) and having a high pressure drop, preferably of the order of 300 mm of water The sections 40 and 42 are wrapped 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 in a longitudinal material

  dinalement corrugated 44, the passages 66 and 68 ending in an upstream zone 67 as in Figure 6 A rod or column of tobacco 12 is fixed on the set of filter using a cape constituted

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

  As indicated by the arrows highlighting the

  smoke, the operation of the filter while a cigarette

  Rette is smoked, is similar to what has been described for Figure 6 The initial flow of smoke passes through the material of the buffer 42 and through the barrier 3 to reach the passages 66, but it is derived gradually to the way through buffers 40 and 42, with increased ventilation

  through passages 68.

  Another embodiment is obtained by reversing, end to end, the structure of FIG. 8, the tobacco rod 12

abutting the buffer 40.

  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

  Sages 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

  smoke, both passages 66 and 68 are available for a

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

by external passages.

  In addition, in FIGS. 6 to 8, the outer envelope (tip cap) 14 may not produce a ventilation effect, the transfer of the smoke flow from the low pressure loss channels to the high pressure drop still ensuring equalization of the taste transmission from one puff to another; in the absence of air dilution, the embodiments of the

  Figures 6 and 8 could also remain essentially

  As has already been described, whether or not the envelope 44 is permeable or perforated, but as previously mentioned, the embodiment of FIG. 7 would be provided with a groove 77.

  closed with a filling portion 80, optionally absent -

  in which case the envelope 44 could be permeable to smoke or perforated Also, in all the embodiments shown

  and / or described, with or without air dilution, the orientation of the

  the filter element in relation to the tobacco rod could be

  However, in some examples of such an inverted structure (for example, that of FIG. 8), if an air dilution was established through the cape of mouthpiece, the ventilation air would

  obliged to pass, when closing the barrier 3, in direc-

  tion of the tobacco tip and then through the nucleus instead of flowing along the more direct initial path towards the end

oral.

  Instead of using intrinsically material sheets

  permeable to smoke which are clogged during use for

  For a transfer of the smoke flow from the low pressure loss lanes to the high pressure loss lanes, a buffer surround may be used with small perforations which are progressively obstructed to produce the same effect. embodiment shown, the barrier 3 could be replaced by a buffer surround formed of a material impervious to smoke and having perforations provided at the ends

  downstream of the smoke bypass passage (s).

  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 attached to the barrier sleeve 3, but the necessary degree of impermeability, and the extent, of the surface of the section of high pressure drop 40 can be established in other ways, as indicated above. 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 process in which rods of even multiple lengths (i.e., each rod is an even multiple of the element or final individual filter) are cut off, the rods of multiple lengths being further subdivided into double length, then, during the production of filter cigarettes, in

  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 FIG.

  and 2, can be produced by first cutting halfway through

  distance of 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 the positions 84. FIG. 13 represents a six-fold length rod which can be cut in a similar way first at 82 mid-way through the inner tubular members 61, then at 84 half way through the high pressure drop members 40 to then produce individual elements. filters and filter cigarettes 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 shown in Figure 8 In Figures 13 and 14, the tip of thermoplastic material 80 of the final products has not been shown, this tip 80 could be set - Place locally in the corresponding areas in a partial operation involved in the continuous manufacture of the rod; he

  could also be put in place on sections of stem de-lon-

  multiple feeds, or on rod sections of double length or single length, before, during or after the incorporation of said sections to filter cigarettes. Referring to FIGS. 12 to 14, it is convenient to realize the form multiple length rods which are suitable for the manufacture of 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

  Development The resulting filters could be attached to cigarettes by ring tips or by tip caps

ventilation.

  The end portions of the paired multiple length rods according to the invention are the parts which abut the tobacco in the final filter cigarettes; thus in the embodiments of Figures 6 to 8, the continuous rod that is produced

  initially is divided into multiple length pairs

  respectively through core sections 61 (FIG. 6) 40 (FIG.

  7) and 42 (Figure 8), these appearing at the ends of

  multiple lengths of double lengths and therefore constituting

* what are the core sections of the final unit lengths which

  come up against the tobacco in the final filter cigarette.

  To obtain filter cigarettes whose elements have the

  reverse, simply cut the continuous rods

  in the positions offset longitudinally with respect to the aforementioned positions of a unit element length, that is to say respectively core sections 40 (Figure 6), 61 (Figure 7) and

40 (Figure 8).

  It should be noted that, to clarify the representation, the drawings are not to scale, at least for the most part; As a result, the radial depth of the undulations 46 and 48 of FIGS. 4 and 5 is greatly exaggerated and their number and core diameter are correspondingly reduced in practice in all embodiments using a corrugated sleeve. substantially all of the diameter (about 8 mm) of the filter element or filter according to the invention is usually occupied 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 indicated

  Figure 11 In the places where only one

  ventilation ratio 16 for each external passage (56 or 58),

  perforations may be more closely spaced, two corrugations

  or more communicating with each of said passages.

  Although figures 4 to it use an imperial 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, preferably with profiled impression rollers; the surfaces of the paper could be left smooth in the

  zones o must end the passages formed by the envelope.

  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 generate a pressure drop for example in Figures 4 to 11, the buffer 40 could be replaced by a buffer not exerting a

  filtering effect and including peripheral and / or

  dusts for substantially unfiltered smoke passage in front of and / or through said buffer, but producing a relatively high pressure drop In such cases, the increased ventilation during the transfer of smoke from low pressure loss pathways to high pressure loss paths may be accompanied by a

  low or no increase in the filtration effect.

  As indicated above, a filter or filter element according to the invention may comprise a recess or cavity at the mouth end; for example, in Figure 4, the core 2

  can end at a short distance from end 50 It is obvious

  dent that the initial path with low pressure drop can communicate directly with such a recess or cavity for example on the

  Figure 4 buffer 42 could be deleted.

  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 elements are arranged integrally end to end, each element or unit 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 in FIGS. 13 and 14 (and compared to length elements

  of Figures 6 and 8), for example, we realize, however, that

  these elements do not have the filling part 80

  which constitutes a necessary part of the elements of uniform length

  at least when they are incorporated in filter cigarettes.

  The invention therefore also relates to

  and multiple length (and unit) filters in the absence of such a fill portion 80 or a similar portion that may be required in the filter cigarette to provide the necessary increase in air dilution with switching the smoke flow from the low pressure loss channels

  to high pressure pathways.

  The filling part 80, when it has to act as a multi-length rod part, could for example be placed locally on the barrier 3 by printing before this barrier is wrapped around the core during the initial production of the rod. keep on going; a permeable envelope could, if necessary, be put in place around the element of

  resulting composite core and the surrounding barrier (preferably

  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 internal and external longitudinal passages which must terminate at the same place, the passages may thus be terminated by a circumferential corrugation of the sleeve. For example, in FIGS. 6 and 8, the smooth part of the envelope 44 and the filling 80 could be replaced by a

  or several circumferential corrugations in the envelope

  pe 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 undulating parts.

-18-

  Although we have involved in the description given

  above a barrier which can be closed by the passage of unfiltered smoke, it goes without saying that the invention is not limited to cases where the smoke in practice reaches the barrier in a totally unfiltered condition. tobacco proper always acts as a filter; in Figure 8, there is necessarily a certain filtration by the buffer 42 while, in other embodiments, the smoke passes directly from the tobacco in the barrier

  and a certain condensation of constituents frequently occurs

  killing smoke upstream of the fence; so it's obvious that we could put a filter material in this part of

  route, for example in passages 66. However, it is preferable

  the filtering effect occurring between the tobacco and the barrier, since otherwise the barrier blocking

an appreciable advantage.

-19-

Claims (7)

  1 filter for tobacco smoke, characterized in that it initially comprises relatively loss-of-way channels   low (8, 3, 2) and relatively high loss-of-way channels.   for the passage of smoke, the or each relatively low-pressure pathway being transversely provided with a barrier (3 which is initially permeable to smoke but which is blocked by the passage of the smoke passing therethrough so that , in service, the initial preferential passage of smoke through the path (s) to   low pressure drop (8, 3, 2) causes a clogging of   so that the passage of smoke through the   or channels with high pressure drop is increased.   2 filter according to claim 1, characterized in that the barrier (3) is formed of a sheet of breathable material with two layers, one layer has an air permeability of between 10 and 100 K, while that the other layer has   an air permeability greater than the first.   3 filter according to claim 2, characterized in that the layer of greater permeability is placed on the downstream face   of the low permeability layer.   4 filter according to any one of claims 1 to 3,   characterized in that it comprises an axially elongated core (2),   having on its periphery at least one passage which extends   firing of one 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 buffer surround (3) which can be closed by the passage of smoke of tobacco passing through it.   Filter according to any one of claims 1 to   3, characterized in that it comprises at least one internal passage   extending from one end of the filter only partially   the other end and in communication, allowing a flow of smoke, with a smoke filtering portion of the filter through a barrier layer (3) which surrounds the passage and separates it from the remainder of the filter, being able   be blocked by the passage of tobacco smoke passing through it.   Filter according to any one of claims 1 to   4, characterized in that it comprises sections of long core   substantially adjacent with relatively large and relatively low pressure losses and surrounded by a profiled sleeve -20- leaving between itself and the core sections one or more passages extending from one end of the filter only partially to the Another end and in that there is provided between the passage (s) and the core section with low pressure drop a barrier which is initially permeable to smoke but which is then closed off by the passage of the tobacco smoke passing through it. . Filter element, characterized in that it comprises   a filter according to any one of claims 1 to 7, without outer envelope.   Filter cigarette, characterized in that it comprises a filter or filter element in accordance with any one of   Claims 1 to 7, incorporated in said cigarette by a cape end cap (14).   Filter or filter element for tobacco smoke of multiple length, characterized in that it comprises several   filters or unit filter elements conforming to any one   conque of claims 1 to 7, which are arranged jointly   end-to-end, each element or unit filter being placed symmetrically   in relation to the or each element or unit filter solidarily adjacent.