(19)
`
`(12)
`
`Europäisches Patentamt
`
`European Patent Office
`
`Office européen des brevets
`
`*EP000703734B1*
`EP 0 703 734 B1
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`(11)
`
`EUROPEAN PATENT SPECIFICATION
`
`(45) Date of publication and mention
`of the grant of the patent:
`14.06.2000 Bulletin 2000/24
`
`(21) Application number: 95915044.2
`
`(22) Date of filing: 06.04.1995
`
`(51) Int Cl.7: A24F 47/00
`
`(86) International application number:
`PCT/US95/04343
`
`(87) International publication number:
`WO 95/27412 (19.10.1995 Gazette 1995/45)
`
`(54) TUBULAR HEATER FOR USE IN AN ELECTRICAL SMOKING ARTICLE
`
`RÖHRENOFEN FÜR EINEN ELEKTRISCHEN RAUCHARTIKEL
`
`DISPOSITIF DE CHAUFFE TUBULAIRE A UTILISER DANS UN ARTICLE ELECTRIQUE POUR
`FUMEURS
`
`(84) Designated Contracting States:
`AT BE CH DE DK ES FR GB GR IE IT LI LU MC NL
`PT SE
`Designated Extension States:
`LT SI
`
`(30) Priority: 08.04.1994 US 224848
`09.01.1995 US 370125
`
`(43) Date of publication of application:
`03.04.1996 Bulletin 1996/14
`
`(73) Proprietor: Philip Morris Products Inc.
`Richmond Virginia 23234 (US)
`
`(72) Inventors:
`• HAJALIGOL, Mohammad R.
`Richmond, VA 23236 (US)
`• FLEISCHHAUER, Grier S.
`Midlothian, VA 23313 (US)
`• DEEVI, Seetharama C.
`Oak Ridge, TN 37830 (US)
`• HIGGINS, Charles T.
`Richmond, VA 23229 (US)
`
`• HAYES, Patrick H.
`Chester, VA 23831 (US)
`• HERMAN, Herbert
`Port Jefferson, NY 11777 (US)
`• GANSERT, Robert V.
`Lake Grove, NY 11755 (US)
`• COLLINS, Alfred L.
`Powhatan, VA 23139 (US)
`• KEEN, Billy J., Jr.
`Chesterfield, VA 23832 (US)
`• LAROY, Bernard C.
`Richmond, VA 23112 (US)
`• LILLY, A. Clinton, Jr.
`Chesterfield, VA 23832 (US)
`
`(74) Representative:
`Lloyd, Patrick Alexander Desmond
`Reddie & Grose
`16 Theobalds Road
`London WC1X 8PL (GB)
`
`(56) References cited:
`EP-A- 0 503 767
`US-A- 5 093 894
`US-A- 5 369 723
`
`WO-A-94/06314
`US-A- 5 322 075
`
`Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give
`notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in
`a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art.
`99(1) European Patent Convention).
`
`Printed by Jouve, 75001 PARIS (FR)
`
`EP0 703 734B1
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`Description
`
`Technical Field of the Invention
`
`[0001] The present invention relates generally to
`heaters for use in an electrical smoking article and more
`particularly to a tubular heater for use in an electrical
`smoking article.
`
`Discussion of the Related Art
`
`[0002] Previously known conventional smoking de-
`vices deliver flavor and aroma to the user as a result of
`combustion of tobacco. A mass of combustible material,
`primarily tobacco, is oxidized as the result of applied
`heat with typical combustion temperatures in a conven-
`tional cigarette being in excess of 800° C during puffing.
`Heat is drawn through an adjacent mass of tobacco by
`drawing on the mouth end. During this heating, ineffi-
`cient oxidation of the combustible material takes place
`and yields various distillation and pyrolysis products. As
`these products are drawn through the body of the smok-
`ing device toward the mouth of the user, they cool and
`condense to form an aerosol or vapor which gives the
`consumer the flavor and aroma associated with smok-
`ing.
`[0003] Conventional cigarettes have various per-
`ceived drawbacks associated with them. Among them
`is the production of sidestream smoke during smolder-
`ing between puffs, which may be objectionable to some
`non-smokers. Also, once lit, they must be fully con-
`sumed or be discarded. Relighting a conventional ciga-
`rette is possible but is usually an unattractive prospect
`for subjective reasons (flavor, taste, odor) to a discern-
`ing smoker.
`[0004] Prior alternatives to the more conventional cig-
`arettes include those in which the combustible material
`itself does not directly provide the flavorants to the aer-
`osol inhaled by the smoker. In these smoking articles, a
`combustible heating element, typically carbonaceous in
`nature, is combusted to heat air as it is drawn over the
`heating element and through a zone which contains
`heatactivated elements that release a flavored aerosol.
`While this type of smoking device produces little or no
`sidestream smoke, it still generates products of com-
`bustion, and once lit it is not adapted to be snuffed for
`future use in the conventional sense.
`[0005]
`In both the more conventional and carbon ele-
`ment heated smoking devices described above com-
`bustion takes place during their use. This process nat-
`urally gives rise to many by-products as the combusted
`material breaks down and interacts with the surrounding
`atmosphere.
`[0006] Commonly assigned U.S. Patent Nos.
`5,093,894; 5,225,498; 5,060,671 and 5,095,921 dis-
`close various electrical resistive heating elements and
`flavor generating articles which significantly reduce
`sidestream smoke while permitting the smoker to selec-
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`tively suspend and reinitiate smoking. However, the cig-
`arette articles disclosed in these patents are not very
`durable and may collapse, tear or break from extended
`or heavy handling. In certain circumstances, these prior
`cigarette articles may crush as they are inserted into the
`electric lighters. Once they are smoked, they are even
`weaker and may tear or break as they are removed from
`the lighter.
`[0007]
`International patent application WO 94/06314,
`describes an electrical smoking system including a nov-
`el electrically powered lighter and novel cigarette that is
`adapted to cooperate with the lighter. The preferred em-
`bodiment of the lighter includes a plurality of metallic si-
`nusoidal heaters disposed in a configuration that slid-
`ingly receives a tobacco rod portion of the cigarette.
`[0008] The preferred embodiment of the cigarette of
`WO 94/06314 preferably comprises a tobacco-laden tu-
`bular carrier, cigarette paper overwrapped about the tu-
`bular carrier, an arrangement of flow-through filter plugs
`at a mouthpiece end of the carrier and a filter plug at the
`opposite (distal) end of the carrier, which preferably lim-
`its air flow axially through the cigarette. The cigarette
`and the lighter are configured such that when the ciga-
`rette is inserted into the lighter, and as individual heaters
`are activated for each puff, localized charring occurs at
`spots about the cigarette in the locality where each heat-
`er was bearing against the cigarette. Once all the heat-
`ers have been activated, these charred spots are closely
`spaced from one another and encircle a central portion
`of the carrier portion of the cigarette. Depending on the
`maximum temperatures and total energies delivered at
`the heaters, the charred spots manifest more than mere
`discolorations of the cigarette paper. In most applica-
`tions, the charring will create at least minute breaks in
`the cigarette paper and the underlying carrier material,
`which breaks tends to mechanically weaken the ciga-
`rette. For the cigarette to be withdrawn from the lighter,
`the charred spots must be at least partially slid past the
`heaters. In aggravated circumstances, such as when
`the cigarette is wet or toyed with or twisted, the cigarette
`may be prone to break or leave pieces upon its with-
`drawal from the lighter. Pieces left in the lighter fixture
`can interfere with the proper operation of the lighter and/
`or deliver an off-taste to the smoke of the next cigarette.
`If the cigarette breaks in two while being withdrawn, the
`smoker may be faced not only with the frustration of
`failed cigarette product, but also with the prospect of
`clearing debris from a clogged lighter before he or she
`can enjoy another cigarette.
`[0009] The preferred embodiment of the cigarette of
`WO 94/06314 is essentially a hollow tube between the
`filter plugs at the mouthpiece end of the cigarette and
`the plug at the distal end. This construction is believed
`to elevate delivery to the smoker by providing sufficient
`space into which aerosol can evolve off the carrier with
`minimal impingement and condensation of the aerosol
`on any nearby surfaces.
`[0010] Several proposals have been advanced which
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`significantly reduce undesired sidestream smoke while
`permitting the smoker to suspend smoking of the article
`for a desired period and then to resume smoking. For
`example, commonly assigned U.S. Patent Nos.
`5,093,894; 5,225,498; 5,060,671 and 5,095,921 dis-
`close various heating elements and flavor generating ar-
`ticles. WO 94/06314 discloses an electrical smoking ar-
`ticle having heaters which are actuated upon sensing of
`a draw by control and logic circuitry. The heaters are
`preferably a relatively thin serpentine structure to trans-
`fer adequate amounts of heat to the cigarette and is
`lightweight.
`[0011] Although these devices and heaters overcome
`the observed problems and achieve the stated objec-
`tives, many embodiments are plagued by the formation
`of a significant amount of condensation formed as the
`tobacco flavor medium is heated to form vapors. These
`vapors can cause problems as they condense on rela-
`tively cooler various electrical contacts and the associ-
`ated control and logic circuitry. In addition, condensation
`can influence the subjective flavor of the tobacco medi-
`um of the cigarette. Though not desiring to be bound by
`theory, it is believed that the condensation is the result
`of the flow pattern and pressure gradient of ambient air
`drawn through the article and the current designs of the
`heater assemblies. The heating of the tobacco flavor
`medium releases vapors which are then cooled to result
`in condensation on the surfaces of relatively cooler com-
`ponents. The condensation can cause shorting and oth-
`er undesired malfunctions.
`[0012]
`In addition, the proposed heaters are subject
`to mechanical weakening and possible failure due to
`stresses induced by inserting and removing the cylindri-
`cal tobacco medium and also by adjusting or toying with
`the inserted cigarette.
`[0013] Also, the electrical smoking articles employ
`electrically resistive heaters which have necessitated
`relatively complex electrical connections which can be
`disturbed by insertion and removal of the cigarette.
`[0014] According to the invention there is provided a
`heater for use in a smoking article having a source of
`electrical energy for heating tobacco flavor medium, the
`heater comprising:
`
`a substrate of electrically conducting material;
`an electrical insulator deposited on at least a portion
`of said substrate; and
`an electrically resistive heater element deposited
`on said electrical insulator, a first end of said heater
`element being electrically connected to said electri-
`cally conducting substrate, wherein a second end
`of said heater element and a portion of said heater
`element between the first and second ends of said
`heater element are electrically insulated from said
`electrically conducting substrate by said insulator,
`wherein said substrate and said second end of said
`heater element are adapted to be electrically con-
`nected to the source of electrical energy, wherein a
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`resistive heating circuit is formed to heat said heat-
`ing element, which in turn heats the tobacco flavor
`medium.
`
`[0015] The invention also provides a heater for use in
`a smoking article having a source of electrical energy
`for heating a cylindrical cigarette, the heater comprising:
`
`a cylindrical tube, of an electrically conducting ma-
`terial, and provided with a plurality gaps there-
`through to define (a) a plurality of electrically con-
`ducting blades defining a receptacle to receive an
`inserted cylindrical cigarette and (b) an electrically
`conducting, common end hub supported within the
`smoking article, the blades extending from the end
`hub;
`an electrical insulator deposited on at least one of
`the plurality of electrically conducting blades;
`an electrically resistive heater element deposited
`on said insulator, a first end of said heater element
`being electrically connected to the at least one of
`the plurality of electrically conducting blades, and
`the second end of said heater element and a portion
`of said heater element between the first and second
`ends are electrically insulated from said at least one
`electrically conducting blade by said insulator;
`wherein said end hub is adapted for electrical con-
`tact with the source of electrical energy, and the
`second end of said heater element is adapted for
`electrical contact with the source of electrical ener-
`gy whereby on electrical contact of the end hub and
`the second end a resistive heating circuit is formed
`to heat said electrically resistive heater element,
`which in turn heats the inserted cigarette.
`
`[0016] The invention further provides a method of
`forming a heater for use in an electrical smoking article
`for heating a cylindrical cigarette, the method compris-
`ing the steps of:
`
`providing an electrically conducting material; form-
`ing (a) a plurality of blades from the electrically con-
`ducting material having gaps therebetween, and (b)
`a common end section, the blades extending from
`the common end section;
`forming an electrical insulator on at least one of the
`plurality of electrically conducting blades;
`forming an electrically resistive heater on the
`formed electrical insulator such that a first end of
`the heater is in electrical contact with the at least
`one electrically conducting blade;
`forming an electrical contact on a second end of the
`formed heater; and
`forming the plurality of blades and the common sec-
`tion into a cylindrical receptacle to receive an insert-
`ed cigarette.
`
`[0017] A heater embodying the invention has the ad-
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`Ex. 2020-0003
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`vantage of generating from a tobacco medium without
`sustained combustion.
`[0018] Embodiments of the invention may have the
`advantag that they reduce the creation of undesired
`sidestream smoke, and the further advantage of permit-
`ting the smoker to suspend and resume use.
`[0019] Furthermore, the above mentioned advantag-
`es may be obtained while reducing aerosol or smoke
`condensation within the smoking article.
`[0020] A preferred embodiment of the invention may
`have the advantage of providing a desired number of
`puffs and which may be modified straightforwardly to
`change the number and or duration of puffs provided
`without sacrificing subjective qualities of the tobacco.
`[0021] Embodiments of the invention may have the
`advantage of providing a heating element for a smoking
`article which is mechanically suitable for insertion and
`removal of a cigarette; which simplify connections of an
`electrically resistive heater to an associated power
`source; and which provide a heater which is more eco-
`nomical to manufacture. Preferably these advantages
`are achieved in a simple and straightforward manner.
`[0022]
`In a preferred embodiment of the invention, a
`cylindrical tube is provided of a mechanically strong and
`flexible electrical conductor such as a metal and has a
`plurality of separated regions. An electrically insulating
`layer such as a ceramic is applied on the outer surface
`except for one exposed portion. Electrically resistive
`materials are then applied to the insulated regions and
`are electrically connected at one end to the underlying
`electrical conducting region to form heater elements.
`This electrical conducting region is connected to the
`negative terminal of a power source. The other end of
`all the heaters are adapted to be connected to the pos-
`itive terminal of the source. Accordingly, an electrically
`resistive heating circuit is formed wherein the tube
`serves as a common for all of the heating elements.
`[0023] The tubular heater can comprise an exposed
`end hub with a plurality of blades extending therefrom.
`Each blade can have an individual heater deposited
`thereon. Alternatively, every other blade can have a
`heater deposited thereon. The blades having no heater
`function as barriers to minimize outward escape of gen-
`erated vapors. These barrier blades also function as
`heat sinks for the heaters on adjacent blades.
`[0024] Embodiments of the invention will now be de-
`scribed, by way of example, and with reference to the
`accompanying drawings, in which:
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`[0025]
`
`FIG. 1 is a partially exposed perspective view of a
`smoking article employing a heater embodying the
`present invention;
`FIG. 2 is a side, cross-sectional view of a cigarette
`used in conjunction with an embodiment of the
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`present invention;
`FIG. 3 is a side, cross-sectional view of a heater
`fixture embodying the present invention;
`FIG. 4 is an exposed side view of a tubular heater
`embodying the present invention;
`FIG. 5 is an exposed side view of a heater blade
`having a metal substrate;
`FIG. 6A is a perspective view of dual hubs having
`a plurality of alternating barrier and heater blades
`extending therebetween;
`FIG. 6B is an embodiment similar to that of FIG. 6A
`except that the gaps between blades are shaped as
`an elongated U;
`FIG. 7 is a perspective view of the embodiment de-
`picted in FIG. 6A having heater elements deposited
`on every defined blade;
`FIG. 8 is a perspective view of a heater having a
`single supporting hub;
`FIG. 9 is a perspective view of tubular heater having
`spiralled gaps;
`FIG. 10 is an exposed side view of a tubular heater
`having heater elements on inner faces of heater
`blades;
`FIG. 11 is a perspective view of an arrangement of
`heater blades prior to rolling;
`FIG. 12 is a perspective of view of a tubular heater
`having a common blade;
`FIG. 13 is a top view of an arrangement of heater
`blades prior to folding; and
`FIG. 14 is a perspective view of another arrange-
`ment of a tubular heater.
`
`DETAILED DESCRIPTION OF BEST MODE
`
`[0026] A smoking system 21 embodying the present
`invention is generally seen with reference to FIGS. 1 and
`2. The smoking system 21 includes a cylindrical aerosol
`generating tube or cigarette 23 and a reusable lighter
`25. The cigarette 23 is adapted to be inserted in and
`removed from an orifice 27 at a front end 29 of the lighter
`25. The smoking system 21 is used in much the same
`fashion as a conventional cigarette. The cigarette 23 is
`disposed of after one or more puff cycles. The lighter 25
`is preferably disposed of after a greater number of puff
`cycles than the cigarette 23.
`[0027] The lighter 25 includes a housing 31 and has
`front and rear portions 33 and 35. A power source 37
`for supplying energy to heating elements for heating the
`cigarette 23 is preferably disposed in the rear portion 35
`of the lighter 25. The rear portion 35 is preferably adapt-
`ed to be easily opened and closed, such as with screws
`or with snap-fit components, to facilitate replacement of
`the power source 37. The front portion 33 preferably
`houses heating elements and circuitry in electrical com-
`munication with the power source 37 in the rear portion
`35. The front portion 33 is preferably easily joined to the
`rear portion 35, such as with a dovetail joint or by a sock-
`et fit. The housing 31 is preferably made from a hard,
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`Ex. 2020-0004
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`heat-resistant material. Preferred materials include met-
`al-based or, more preferably, polymer-based materials.
`The housing 31 is preferably adapted to fit comfortably
`in the hand of a smoker and, in a presently preferred
`embodiment, has overall dimensions of 10.7 cm by 3.8
`cm by 1.5 cm.
`[0028] The power source 37 is sized to provide suffi-
`cient power for heating elements that heat the cigarette
`23. The power source 37 is preferably replaceable and
`rechargeable and may include devices such as a capac-
`itor, or more preferably, a battery. In a presently pre-
`ferred embodiment, the power source is a replaceable,
`rechargeable battery such as four nickel cadmium bat-
`tery cells connected in series with a total, non-loaded
`voltage of approximately 4.8 to 5.6 volts. The character-
`istics required of the power source 37 are, however, se-
`lected in view of the characteristics of other components
`in the smoking system 21, particularly the characteris-
`tics of the heating elements. U.S. Patent No. 5,144,962
`describes several forms of power sources useful in con-
`nection with the smoking system of the present inven-
`tion, such as rechargeable battery sources and quick-
`discharging capacitor power sources that are charged
`by batteries.
`[0029] A substantially cylindrical heating fixture 39 for
`heating the cigarette 23, and, preferably, for holding the
`cigarette in place relative to the lighter 25, and electrical
`control circuitry 41 for delivering a predetermined
`amount of energy from the power source 37 to heating
`elements (not seen in FIGS. 1 and 2) of the heating fix-
`ture are preferably disposed in the front 33 of the lighter.
`As described in greater detail below, a generally circular,
`terminal end hub 110 is fixed, e.g., welded, to be dis-
`posed within the interior of heater fixture 39, e.g., is fixed
`to spacer 49, as shown in FIG. 3. If the heater has two
`end hubs, either hub can serve as the fixed terminal end.
`In the presently preferred embodiment, the heating fix-
`ture 39 includes a plurality of radially spaced heating
`elements 122 supported to extend from the hub, seen
`in FIG. 3 and described in greater detail below, that are
`individually energized by the power source 37 under the
`control of the circuitry 41 to heat a number of, e.g., eight,
`areas around the periphery of the inserted cigarette 23.
`Eight heating elements 122 are preferred to develop
`eight puffs as in a conventional cigarette and eight heat-
`er elements also lend themselves to electrical control
`with binary devices. A desired number of puffs can be
`generated, e.g., any number between 5-16, and prefer-
`ably 6-10 or 8 per inserted cigarette. As discussed be-
`low, the number of heaters can exceed the desired
`number of puffs/cigarette.
`[0030] The circuitry 41 is preferably activated by a
`puff-actuated sensor 45, seen in FIG. 1, that is sensitive
`either to pressure drops that occur when a smoker
`draws on the cigarette 23. The puff-actuated sensor 45
`is preferably disposed in the front 33 of the lighter 25
`and communicates with a space inside the heater fixture
`39 and near the cigarette 23 through a passageway ex-
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`tending through a spacer and a base of the heater fixture
`and, if desired, a puff sensor tube (not shown). A puff-
`actuated sensor 45 suitable for use in the smoking sys-
`tem 21 is described in U.S. Patent No. 5,060,671, and
`is in the form of a Model 163PC01D35 silicon sensor,
`manufactured by the MicroSwitch division of Honeywell,
`Inc., Freeport, Illinois, which activates an appropriate
`one of the heater elements 122 as a result of a change
`in pressure when a smoker draws on the cigarette 23.
`Flow sensing devices, such as those using hot-wire an-
`emometry principles, have also been successfully dem-
`onstrated to be useful for activating an appropriate one
`of the heater elements 122 upon detection of a change
`in air flow.
`[0031] An indicator 51 is preferably provided on the
`exterior of the lighter 25, preferably on the front 33, to
`indicate the number of puffs remaining on a cigarette 23
`inserted in the lighter. The indicator 51 preferably in-
`cludes a seven-segment liquid crystal display. In a pres-
`ently preferred embodiment, the indicator 51 displays
`the digit "8" for use with an eight-puff cigarette when a
`light beam emitted by a light sensor 53, seen in FIG. 1,
`is reflected off of the front of a newly inserted cigarette
`23 and detected by the light sensor. The light sensor 53
`is preferably mounted in an opening in the spacer and
`the base of the. heater fixture 39. The light sensor 53
`provides a signal to the circuitry 41 which, in turn, pro-
`vides a signal to the indicator 51. For example, the dis-
`play of the digit "8" on the indicator 51 reflects that the
`preferred eight puffs provided on each cigarette 23 are
`available, i.e., none of the heater elements 43 have
`been activated to heat the new cigarette. After the cig-
`arette 23 is fully smoked, the indicator displays the digit
`"0". When the cigarette 23 is removed from the lighter
`25, the light sensor 53 does not detect the presence of
`a cigarette 23 and the indicator 51 is turned off. The light
`sensor 53 is modulated so that it does not constantly
`emit a light beam and provide an unnecessary drain on
`the power source 37. A presently preferred light sensor
`53 suitable for use with the smoking system 21 is a Type
`OPR5005 Light Sensor, manufactured by OPTEX Tech-
`nology, Inc., 1215 West Crosby Road, Carroliton, Texas
`75006 U.S.A.
`[0032] As one of several possible alternatives to using
`the above-noted light sensor 53, a mechanical switch
`(not shown) may be provided to detect the presence or
`absence of a cigarette 23 and a reset button (not shown)
`may be provided for resetting the circuitry 41 when a
`new cigarette is inserted in the fighter 25, e.g., to cause
`the indicator 51 to display the digit "8", etc. Power sourc-
`es, circuitry, puff-actuated sensors, and indicators use-
`ful with the smoking system 21 of the present invention
`are described in U.S. Patent No. 5,060,671 and WO
`94/06314, both of which are incorporated by reference.
`The passageway and the opening 50 in the spacer and
`the heater fixture base are preferably air-tight during
`smoking.
`[0033] A presently preferred cigarette 23 for use with
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`Ex. 2020-0005
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`the smoking system 21 will now be described and is
`shown in greater detail in the above-mentionad WO
`94/06314, although the cigarette may be in any desired
`form capable of generating a flavored tobacco response
`for delivery to a smoker when the cigarette is heated by
`the heating elements 122. Referring to FIG. 2, the cig-
`arette 23 includes a tobacco web 57 formed of a carrier
`or plenum 59 which supports tobacco flavor material 61,
`preferably including tobacco. The tobacco web 57 is
`wrapped around and supported by a cylindrical back-
`flow filter 63 at one end and a cylindrical first free-flow
`filter 65 at an opposite end. The first free-flow filter 65
`is preferably an 'open-tube' type filter having a longitu-
`dinal passage 67 extending through the center of the
`first free-flow filter and, hence, provides a low resistance
`to draw or free flow.
`[0034]
`If desired, cigarette overwrap paper 69 is
`wrapped around the tobacco web 57. Types of paper
`useful as the overwrap paper 69 include a low basis
`weight paper, preferably a paper with a tobacco flavor
`coating, or a tobacco-based paper to enhance the to-
`bacco flavor of a flavored tobacco response. A concen-
`trated extract liquor in full or diluted strength may be
`coated on the overwrap paper 69. The overwrap paper
`69 preferably possesses a minimal base weight and cal-
`iper while providing sufficient tensile strength for ma-
`chine processes. Presently preferred characteristics of
`a tobacco-based paper include a basis weight (at 60%
`relative humidity) of between 20-25 grams/m2, minimum
`permeability of 0-25 CORESTA (defined as the amount
`of air, measured in cubic centimeters, that passes
`through one square centimeter of material, e.g., a paper
`sheet, in one minute at a pressure drop of 1.0 kilopas-
`cal), tensile strength 2 2000 grams/27 mm width (1 in/
`min), caliper 1.3-1.5 mils (about 0.03mm - 0.04mm),
`CaCO3 content ≤ 5%, citrate 0%. Materials for forming
`the overwrap paper 69 preferably include ≥ 75% tobac-
`co-based sheet (non-cigar, flue- or fluelair-cured mix fill-
`er and bright stem). Flax fiber in amounts no greater
`than that necessary to obtain adequate tensile strength
`may be added. The overwrap paper 69 can also be con-
`ventional flax fiber paper of basis weight 15-20 g/m2 or
`such paper with an extract coating. Binder in the form
`of citrus pectin may be added in amounts less than or
`equal to 1%. Glycerin in amounts no greater than nec-
`essary to obtain paper stiffness similar to that of con-
`ventional cigarette paper may be added.
`[0035] The cigarette 23 also preferably includes a cy-
`iindrical mouthpiece filter 71, which is preferably a con-
`ventional RTD-type (Resistance To Draw) filter, and a
`cylindrical second free-flow filter 73. The mouthpiece fil-
`ter and the second free-flow filter are secured to one
`another by tipping paper 75. The tipping paper 75 ex-
`tends past an end of the second free-flow filter 73 and
`is attached to the overwrap paper 69 to secure an end
`of the first free-flow filter 65 in position adjacent an end
`of the second free-flow filter 73. Like the first free-flow
`filter 65, the second free-flow filter 73 is preferably
`
`5
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`6
`
`formed with a longitudinal passage 77 extending
`through its center. The back-flow filter 63 and the first
`free-flow filter 65 define, with the tobacco web 57, a cav-
`ity 79 within the cigarette 23.
`[0036]
`It is preferred that the inside diameter of the
`longitudinal passage 77 of the second free-flow filter 73
`be larger than the inside diameter of the longitudinal
`passage 67 of the first free-flow filter 65. Presently pre-
`ferred inside diameters for the longitudinal passage 67
`are between 1-4 mm and for the longitudinal passage
`77 are between 2-6 mm. It has been observed that the
`different inside diameters of the passages 67 and 77 fa-
`cilitates development of a desirable mixing or turbulence
`between the aerosol developed from the heated tobac-
`co flavor material and air drawn in from outside the cig-
`arette 23 during drawing on the cigarette, resulting in an
`improved flavored tobacco response and facilitating ex-
`posure of more of an end of the mouthpiece filter 71 to
`the mixed aerosol. The flavored tobacco response de-
`veloped by heating the tobacco flavor material 61 is un-
`derstood to be primarily in a vapor phase in the cavity
`79 and to turn into a visible aerosol upon mixing in the
`passage 77. In addition to the above-described first free-
`flow filter 65 having a longitudinal passage 67, other ar-
`rangements capable of generating the desired mixing of
`the vapor phase flavored tobacco response with intro-
`duced air include those in which a first free-flow filter is
`provided in the form of a filter having a multitude of small
`orifices, i.e., the first free-flow filter may be in the form
`of a honeycomb or a metal plate having multiple holes
`formed therein.
`[0037] Air is preferably drawn into the cigarette 23
`predominantly through the tobacco web 57 and the
`overwrap paper 69, in a transverse or radial path, and
`not through the back-flow filter 63 in a longitudinal path.
`It is desirable to permit air flow through the back-flow
`filter 63 during a first puff on the cigarette to lower the
`RTD. It is presently understood that drawing air into the
`cigarette 23 longitudinally tends to result in the aerosol
`developed by heating the tobacco web with the heater
`elements 122 arranged radially around the tobacco web
`not being properly removed from the cavity 79. It is pres-
`ently preferred to produce a flavored tobacco response
`as a function almost entirely of the makeup of the tobac-
`co web 57 and the energy level of the heater elements
`122. Accordingly, the portion of the air flow through the
`cigarette resulting from longitudinal flow through the
`backflow filter 63 is preferably minimal during smoking,
`except during the first puff. Further, the back-flow filter
`63 preferably minimizes the flow of aerosol in a back-
`ward direction out of the cavity 79 after heating of the
`tobacco flavor material 61, so that the potential for dam-
`age to components of the lighter 25 from aerosol flowing
`backward from the cigarette 23 is minimized.
`[0038] The carrier or plenum 59 which supports the
`tobacco flavor material provides a separation between
`the heating elements 122 and the flavor material, trans-
`fers heat generated by the heater elements to the flavor
`
`Ex. 2020-0006
`
`

`

`11
`
`EP 0 703 734 B1
`
`12
`
`material, and maintains cohesion of the cigarette after
`smoking. Preferred carriers 59 include those composed
`of a non-woven carbon fiber mat, preferred because of
`its thermal stability. Such carriers are discussed in great-
`er detail in WO 94/06314.
`[0039] Other carriers 59 include low mass, open mesh
`metallic screens or perforated metallic foils. For exam-
`ple, a screen having a mass in the range from about 5
`g/m2 to about 15 g/m2 and having wire diameters in the
`range from about 0.038 mm (about 1.5 mils) to about
`0.076 mm (about 3.0 mils) is used. Another embodiment
`of the screen is formed of a 0.0064 mm (about 0.25 mil)-
`thick foil (e.g., aluminum) having perforations with diam-
`eters in the range from about 0.3 mm to about 0.5 mm,
`to reduce the mass of the foil by about 30 percent to
`about 50 percent, respectively. Preferably, the perfora-
`tion pattern of such a foil is staggered or discontinuous
`(i. e., not in straight arrangement) to reduce the lateral
`conduction of heat away from the tobacco