AU592109B2 - Smoking article - Google Patents

Abstract

A member is provided for conducting heat from a combustible fuel element to an 'aerosol' generator which includes aerosol-forming material. The conducting member is spaced from the lighting end of the fuel element by at least 5 mm., and can circumscribe both the fuel element and generator, at least partially. Alternatively, the conductor contacts the fuel element along less than approx. half its length, e.g. it is embedded within it. Pref. the fuel element has a length of less than approx. 30 mm and has a density of about 0.5 g/cc.

Description

FORM 10 Class 592 09 SPRUSON FERGUSON COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952 COMPLETE SPECIFICATION

(ORIGINAL)

FOR OFFICE USE: Int. Class Complete Specification Lodged: Accepted: Published: 'rs r n-nt contains lbs ainneuanots znsde under Section 49.

and Is Dorrect tor printba.

Priority: Related Art: Name of Applicant: S Address of Applicant; Actual Inventor(s): R. J. REYNOLDS TOBACCO COMPANY 403 North Main Street, Winston-Salem, North Carolina 27102, United States of America CHANDRA KUMAR BANERJEE, ERNEST GILBERT FARRIER, JAMES LUTHER HARRIS, ALAN BENSON NORMAN, JAMES LEE RESCE, JOHN HUGHES REYNOLDS IV, HENRY THOMAS RIDINGS, ANDREW JACKSON SENSABAUGH, JR., MICHAEL DAVID SHANNON and GARY ROGER SHELAR Address for Service: Spruson Ferguson, Patent Attorneys, Level 33 St Martins Tower, 31 Street, Sydney, New South ales, 2000, Australia Market Complete Specification for the invention entitled: "SMOKING ARTICLE" The following statement Is a full description of this invention, including the best method of performing it known to us SBR/JS/0175W E,3 IC C 1 r~-

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2 SMOKING ARTICLE BACKGROUND OF THE INVENTION The present invention relates to a smoking article, preferably in cigarette form, which produces an aerosol that resembles tobacco smoke, and which advantageously contains substantially reduced amounts of incomplete combustion and pyrolysis products than are noramlly produced by a conventional cigarette.

Many smoking articles have been proposed though the years, especially over the last 20 to 30 years, but none of these products has ever realized any commercial success.

Despite decades of interest :,iu effort, there is still no smoking article on the market which provides the benefits and advantages associated with conventional cigarette smoking, without delivering the considerable quantitites of incomplete combustion and pyrolysis products generated by a conventional cigarette.

It is the object of the present invention to provide a smoking article which produces an aerosol which contains substantailly reduced amounts of incomplete combustion and pyrolysis products than are normally produced by a conventional cigarette.

In one broad form the present invention provides a cigarette-type smoking article comprising a carbonaceous fuel element and a physically separate aerosol generating means including an aerosol forming material, the aerosol generating means being located between the fuel element and the mouthend of the article and further comprising a physically separate tobacco containing mass circumscribing at least a portion of the aerosol generating means.

A further form of the present invention provides a cigarette type smoking article comprising a combustible fuel element having a length of less than 30 mm.; a physically separate aerosol generating means including an aerosol forming material, the physically separate aerosol generating means being located between the fuel element and the mouthend of the article; and further comprising a physically separate tobacco containing mass circumscribing at least a portion of the aerosol generating means.

KLN/1560b 3 A still further broad form of the present invention provides a smoking article comprising a combustible fuel element and a physically separate aerosol generating means including an aerosol forming material, the fuel element including a plurality of longitudinal passageways which are arranged such that during burning they coalesce into a single passageway at least at the lighting end of the fuel element.

As used herein, and only for the purposes of this application, "aerosol" is defined to include vapors, gases, particles, and the like, both visible and invisable, and especially those components perceived by the user to be "smoke-like" generated by r, KLN/ 560b tl*t b H 1 .d t i.ri t:C,,I ,lr if

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action of the heat from the burning fuel element upon substances contained within the aerosol generating means, or elsewhere in the article. As so defined, the term "aerosol" also includes volatile flavoring agents and/or pharmacologically or physiologically active agents, irrespective of whether they produce a visible aerosol.

As used herein, the term "conductive heat exchange relationship" is defined as a physical arrangement of the aerosol generating means and the fuel element whereby heat is transferred by conduction from the burning fuel element to the aerosol generating means substantially throughout the burning period of the fuel element. Conductive heat exchange relationships can be achieved by locating the aerosol generating means in contact with the fuel element and in close proximity to the burning portion of the fuel element, and/or by utilizing a conductive member to transfer heat from the burning fuel to the aerosol generating 20 means. Preferably both methods of providing conductive heat transfer are used.

As used herein, the term "insulating member" applies to all materials which act primarily as insulators. Preferably, these materials do not burn during use, but they may include slow burning carbons and like materials, and especially materials which fuse during use, such as low temperature grades of glass fibers.

Suitable insulators have a thermal conductivity in g-cal/(sec) (cm2)( C/cm), of less than about 0.05, preferably less than about 0.02, most preferably less than about 0.005. See, Hackh's Chemical Dictionary, 34 (4th ed., 1969) and Lange's Handbook of Chemistry, 272-274 (11th ed., 1973).

Spe- forvs cyp The smoking article of the present invention i~ described in greater detail in the accompanying Ut I I U I it I I I it (Cr

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I U U Uj Ut U 4U U Ut U U b ;i:I ;i drawings and in the detailed description of the invention which follow.

BRIEF DESCRIPTION OF THE DRAWINGS Figures 1 through 9 are longitudinal sectional views of various embodiments of the invention; Figure 1A is a sectional view of the embodiment of Figure 1, taken along lines 1A-1A in Figure 1; Figure 2A is a sectional view of the embodiment of Figure 2, taken along lines 2A-2A in Figure 2; Figure 6A is a sectional view of the embodiment of Figure 6, taken along lines 6A-6A in Figure 6; Figures 7A, 7E 7C, and 9A are ena views showing various fuel element passageway configurations suitable for use in embodiments of the invention; Figure 8A is a sectional view of the embodiment cf Figure 8, taken along lines 8-8 in Figure 8; Figure 8B is an enlarged end view of the metallic container employed in the embodiment of 20 Figure 8; and Figure 95 is a longitudinal sectional view of S a preferred fuel element passageway configuration suitable for use in embodiments of the invention.

DETAILED DESCRIPTION OF THE INVENTION The embodiment of the invention illustrated in Figure 1, which preferably has the overall diment sions of a conventional cigarette, includes a short, about 20 mm long, combustible fuel element 10, an abutting aerosol generating means 12, and a foil lined l .o 30 paper tube 14, which forms the mouthend 15 of the article. In this embodiment, fuel element 10 is extruded or molded from a mixture containing comminuted or reconstituted tobacco and/or a tobacco substitute and a minor amount of combustible carbon, and is pro- Vided with five longitudinally extending holes 16. See Figure lA. The lighting end of fuel element 10 may be tapered or reduced in diameter to improve ease of lighting.

Aerosol generating means 12 includes a porous carbon mass 13 which is provided with one or more passages 17 and is impregnated with one or more aerosol i forming materials, such as triethylene glycol, propylene glycol, glycerin, or mixtures thereof.

The foil lined paper tube 14, which forms the mouthend piece of the article, surrounds aerosol generating means 12 and the rear, nonlighting end of fuel element 10 so that the foil lined tube is spaced about 15 mm from the lighting end of the fuel element. The tube 14 also forms an aerosol delivery passage 18 between the aerosol generating means 12 and mouth end of the article. The presence of foil lined tube 14, ,which couples the nonlighting end of fuel 10 to aerosol r 20 generatr 12, increases heat transfer to the aerosol S.generatr. .Te f-l alssc helps to extinguish the fire cone. When only a small amount of the unburned fuel remains, heat loss through the foil acts as a heat sink which helps zc extinguish the fire cone. The foil used in this article is typically an aluminum foil of 0.35 mils (0.0089 mm) in thickness, but the thickness and/or the type of conductor employed may be varied to achieve virtually any desired degree of heat transfer.

The article illustrated in Figure 1 also includes an optional mass or plug of tobacco 20 to contribute flavor to the aerosol. This tobacco charge 20 may be placed at the mouth end of carbon mass 13, as shown in Figure 1, cr it may be placed in passage 18 at a location spaced from aerosol generator 12. For appearance sake, the article may include an optional 7 low efficiency cellulose acetate filler 22, positioned at or near the mouth end The embodiment of the invention illustrated in Figure 2, includes a short combustible fuel element 24, about 20 mm long, connected to aerosol generating means 12 by a heat conductive rod 26 and by a foil lined paper tube 14, which also leads to the mouth end of the article. Aerosol generating means 12 includes a thermally stable carbonaceous substrate 28, such as a plug of porous carbon, which is impregnated with one or more aerosol forming materials. This embodiment includes a void space 30 between the fuel element 24 and the substrate 28. The portion of the foi1 lined tube 14 surrounding this void space includes a plurality of peripheral holes 32 which permit sufficient air to enter the void space to provide appropriate pressure droo.

As shown in Figures 2 and 2A, the heat cont ducting means includes the conductive rod 26 and the S 20 foil lined tube 14, both of which are spaced from the S, lighting end of the fuel element. The rod 26 is spaced it about 5 mmr, from the lighting end; the tube about 15 mm.

'tt The rod 26 is preferably formed of aluminum and has at least one, preferably from 2 to 5, peripheral grooves 34 therein, to allow air passage through the substrate.

The article of Figure 2 has the a.dvantage that the air introduced into void space 30 contains less oxidation S, ,P products because it is not drawn through the burning t fuel.

t| 30 The embodiment illustrated in Figure 3 includes fuel element 10, about 10 mm long, with a single axial hole 16. Again, the lighting end of the fuel element may be tapered or reduced in diameter to improve ease of lighting. The substrate 38 of the aerosol generator is a granular, thermally stable 0'1 q carbon or alumina impregnated with an aerosol forming material. A mass of tobacco 20 is located immediately behind the substrate. This article is provided with a cellulose acetate tube 40, in place of the foil lined tube of previous embodiments. This tube 40 includes an annular section 42 of resilient cellulose acetate tow surrounding an optional plastic tube 44 of polypropylene, Nomex, Mylar, or the like. At the mouth end of this element there is a low efficiency cellulose acetate filter plug The entire length of the article may be wrapped in cigarette-type paper 46. A cork or white ink coating 48 may be used on the mouth end to simulate tipping, A foil strip 50 is located on the inside of the paper, toward the fu~el end of the article. This strip preferaly- overlaps the rear 2 to 3 mm of the .fuel element and ex:tends to the mouth end of the tobacco charge 20, it may be integral with the paper or it may be a separate piece applied. befoi'e the paper 20 overwrapo The embodi.ment of Figure 4 is similar to that of Figure 3. in this embodiment, the fuel element is about 15 hmm long and the aerosol generating means 12 is formed by an aluminum capsule 52. which is filled with a grantular Substrate or, as shown in the drawingi a mixture of a granular substrate 54 and tobarco 56, The capsule 52 is crimped at its ends 58, 60 to enclose the material and. to inhibit migration of the aerosol former. The crimped end 58, at the fuel end, preferably abuts the rear end of the fuel element to provide for conductive heat transfer.

A void space 62 formed by end 58 also helps to inhibit migration of the aerosol former to the fiuel.

Longitudinal passageways 59 and 61 are provided to permit the passage of air and the aerosol forming Material.

C t t.

C 4 C CC I C t. I

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k Capsule 52 and fuel element 10 may be united by a conventional cigarette paper 47, as illustrated in the drawing, by a perforated ceramic paper, or a metallic strip or tube. If cigarette paper is used, a strip 64 near the rear end of the fuel should be printed or treated with sodium silicate or other known materials which cause the paper to extinguish. If a metal foil is used, it preferably should be spaced about 8 to 12 mm from the lighting end of the fuel. The entire length of the article may be overwrapped with conventional cigarette paper 46.

The embodiment shown in Figure 5 illustrates the use of a substrate 66 impregnated with one or more aerosol forming materials and which is embedded within a large cavity 68 in fuel element 10. In this type of embodiment, the substrate 66 usually is a relatively rigid, porous material. The entire length of the article may be wrapped with conventional cigarette paper 46. This embodiment may also include a foil 20 strip 70 to couple flel element 10 to the cellulose acetate tube 40 and to help extinguish the fuel. This strip is spaced about 5 to 10 mm from the lighting end.

j The embodiments shown in Figures 6 through 8 include a resilient insulating jacket which encircles or circumscribes the fuel element to insulate and help concentrate the heat in the fuel element. These embodiments also help to reduce any fire causing potential of the burning fire cone and, in some cases, help A, a simulate the feel of a conventional cigarette.

In the embodiment of Figure 6, the fuel element 10 is provided with a plurality of holes 16 and is circumscribed by a resilient jacket 72 about 0.5 mm thick, as shown in Figure 6A. This jacket is formed of insulating fibers, such as ceramic glass) fibers or nonburning carbon or graphite fibers. The aerosol -1 I_ Io generating means 12 comprises a porous carbon mass 13 having a single, axial hole 17.

In the embodiment of Figure 7, the resilient, glass fiber insulating jacket 72 surrounds the periphery of both fuel element 10 and aerosol generating means 12 and is preferably a low temperature material which fuses during use. This jacket 72 is overwrapped with a non-porous paper 73, such as P 873-5 obtained from Kimberly-Clark. In this embodiment, the fuel element is about 15 to 20 mm long and is preferably provided with three or more holes 16 to increase air flow through the fuel. Three suitable passageway arrangements are illustrated in Figures 7A, 7B, and 7C.

In this embodiment, the aerosol generating means 12 comprises a metallic container 74 which encloses a granular substrate 38 and/or densified tobacco 76, one or both of which include an aerosol forming I, material. As illustrated, the open end 75 of container 74 overlaps the rear 3 to 5 mm portion of fuel element 10, Alternatively, the open end 75 may abut the rear end of fuel element 10. The opposite end of container 74 is crimped to form wall 78, which is provided with a plurality of passages 80 to permit passage of gases, tobacco flavors, and/or the aerosol forming material into aerosol delivery passage 18.

*Plastic tube 44 abuts or preferably overlaps Si walled end 78 of metallic container 74 and is surrounded by a section of resilient, high density cellui lose acetate tow 42. A layer of glue 82, or other material, may be applied to the fuel end of tow 42 to seal the tow and block air flow therethrough. A low efficiency filter plug 45 is provided at the mouth end of the article, and tow 42 and filter plug 45 are preferably overwrapped with a conventional plug wrap paper 85. Another layer of cigarette paper 86 may be /4sAv 1 cc tcrE O

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used to join the rear portion of the insulating jacket 72 and the tow/filter section.

In a modified version of the embodiment of Figure 7, the insulating jacket may also be used in lieu of the cellulose acetate tow 42, so that the jacket extends from the lighting end to the filter plug In embodimen'-s of this type, a layer of glue is preferably applied to the annular section of the filter 1 plug which abuts the end of the insulating jacket, or a short annular section of tow is placed between the insulating jacket and the filter piece, with glue applied at either end.

Figure 8 illustrates an embodiment in which a to 15 mm long fuel element 10 is overwrapped with an i 15 insulating jacket 72 of glass fibers and the aerosol generating means is circumscribad by a jacket of Stobacco 88. The glass fibers used on this embodiment ;j preferably have a softenirq temperature below about .6500C, such as experimental fibers 6432 and 6437 S 20 obtaned from Owens-.Corning, Toledo, Ohio, so that they S, will fuse during use, The glass fiber and tobacco I jackets are each wrapped with a plug wrap 85, such as EcUsta 646, and are joined by an overwrap of cigarette paper 89, such as 78)-63-5 or P 878-16-2, obtained from Kimberiy-Clark. In this embodiment, the metallic l capsule 90 overlaps the rear 3 to 4 mm of the fuel S t. element so that :t is spaced about 6 to 1Z mm from the [,lighting end, and the rear portion of the capsule 90 is crimped into a lobe shape, as shown in Figure 8B, A S 30 passage 91 is provided at the mouth end of the capsule, t in the center of the capsule. Four additional passages 92 are provided at the transition points between the crimped and uncrimped portion of the capsule. Alternatively, the rear portion of the capsule may have a rectangular or square cross section in lieu of the lobes, or a simple tubular capsule with a crimped mouth end may be employed, with or without peripheral passages 92.

At the mouth end of tobacco jacket 88 is a mouthend' piece 40 including an annular section of cellulose acetate tow 42, a plastic tube 44, a low efficiency filter piece 45, and layers of cigarette paper 85 and 89, The mouth end piece 40 is joined to the jacketed fuel/capsule end by an overwrapping layer of tippi4ng paper 86, As illustrated, the capsule end Of pOlastic tube 441 is spaced from the capsule Thus, the hot vapors flowing through passages 92, pass through tobacco Jac~;et 88, where volatile components in the tobacco are %vapcriz,-e-- or extracted, and then into passage where the tob-acco Jac)tabsthceloe acetate tow 42'.

In errbod ,mrts of t'h-is type having low density fue.' an a gJack-ets 72, some air and gases pas:s tnroug'.h 34Qet .7Z and, into tobacco jacket 88, 2 0 Thus, the pe~hrlpassage 92 in the capsule may not be neded to ex-:ract t'acc favor from the tobacco aIne the embodir-ent of Figu~re 9, the jacket 94 c omp r 1se z tobacqo or an admIxture of tobacco and insulatjlng ers:, sunas glass fibers. As shown, the tobaccocke 94 ex-ends just, beyond the mouth end of metalljc container AlternatiVely, it may extend over the entire length of the article, up to the mouth end filter piece, In embodiments of this type, contamner 96 is p-eferably provided With one or more long~itudina* slots 9 on, its periphery (preferably two slots 1800 apart) so that Vapors 4rom the aerosol generator pass through the annular section of tobaco which surroundz the aerosol generator to extract tobacco flavors be-Core entering passage 18, 01 kit As illustrated, the tobacco at the fuel element end of jacket 94 is compressed. This aids in reducing air flow through the tobacco, tht:reby reducing the burn potential thereof. In addition, the container 96 aids in extinguishing the tobacco by acting as a heat sink.. This heal,' sink effect helps quench any burning of the tobacco surrounding the capsule, and it also helps to evlenly distribute heat to the tobacco around the aerosol generating means, thereby aiding in the release of tobacco flavor components. In addition, it may be desirable to treat the portion of the cigarette paper overwrap 85, 89 near the rear end of the fue'L w-,th a material, such as sodium silicate, to help extingu~sh the tobacco, so that it will not burn is significantly beyond the exposed portion of the fuel element, A.lternatively, the tobacco itself may be treated with a burn, modifier to prevent burning of the tobacco whichi surr'ounds the aerosol generator, Upor. lighting any7 of the aforesaid embodi4ments, the fuel element burns, qene.-ating the heat used to vo'Latili e the aerosol forminq material or materials present in the aeroscl qenerat+*nq means, These volatile materials are theon drawn toward the mouthend, especial'y dtiring puf4 i.n, and into the user's mouth, ak-in to the smoke of a conventional cigarette, Because the fuel A--en i relatively short, the hot, burning fire cone is always close the aerosol generating body, whic;h maximizes heat 'ransfer to the aerosol generating MeAns and any optional 30 tobtccQ charges, and the resu~ltanft pr'oduction tf aerosol and optional tobacco flavor, especially whel\ the preferred heat conducting mnemb~er is 'Ased. Because the fuel Olement i.s short, there is never a lonq seetion bof nonburning fqel to act as a 114t itk, 04 WAS common in previous 'thermal aerosol irticles, ""ae t I I It I it fuel source also tends to minimize the amount of incomplete combustion or pyrolysis products, especially in embodiments which contain carbon and/or multiple passageways.

Heat transfer, and therefor aerosol delivery, also is enhanced by the use of passageways through the fuel, which draw hot air to the aerosol generator, especially during puffing. Heat transfer also is enhanced by the preferred heat conducting member, which is spaced or recessed from the lighting end of the fuel element to avoid interference with lighting and burning of the fuel and to avoid any unsightly protrusion, even after use. In addition, the preferred insulating member tends to confine, direct, and concentrate the 13 heat toward the central core of the article, thereby increasing the heat transferred to the aerosol forming substance.

Because the aerosol forming material is physially separate from the fuel element, it is exposed to 20 substantially lower temperatures than are present in I the burning fire cone, This minimizes the possibility *of thermal degradation of the aerosol former and attendar t off taste This also results in aerosol production during puffing, but minimal aerosol production from the aerosol generating means during smolder.

in the preferred embodiments of the invention, the short fuel element, the recessed heat con- Ij ducting member, the insulating member, and/or the passages in the fuel cooperate with the aerosol gene- S 30 rator t.o provide a system which is capable of producing S9 substantial quantities of aerosol and optional tobacco flavor, on virtually every puff. The close proximity of the fire cone to the aerosol generator after a few puffs, together with the conducting member, the insulating member, and/or the multiple passageways in the I I fuel elerent, results in high heat delivery both during puffing and during the relatively long period of smolder between puffs.

While not wishing to be bound by theory, it is believed that the aerosol generating means is maintained at a relatively high temnerature between puffs, and that the additional heat delivered during puffs, which is significantly increased by the preferred passageways in the fuel element, is primarily utilized to vaporize the aerosol forming material. This increased heat transfer makes more efficient use of the available fuel energy, reduces the amount of fuel needed, and helps deliver early aerosol.

Furthermore, by the appropriate selection of the fuel element composition, the number, size, configration, and arrangement of fuel element passageways, the insulating jacket, the paper overwrap, and/or the heat conducting means, it is possible to control the burn properties of the fuel source to a substantial 20 degree, This provides significant control over the heat transferred to the aerosol generator, which in Sturn, can be used to alter the number of puffs and/or the amount of aerosol delivered to the user.

In general, the combustible fuel elements which may be employed in practicing the invention are less than about 30 mm long. Preferably the fuel element is about 20 nm or less, more preferably about mm or less in length. Advantageously, the diameter tot 0' of the fuel element is about 8 mm or less, preferably between about 3 and 7 mm, and more preferably between t' about 4 to 6 mm, The density of the fuel elements ft which may be employed herein range from about 0.5 g/cc to about 1.5 g/cc as measured, by mercury displacement. Preferably, the density is greater than 0.7 g/cc., more preferably greater than 0.8 g/cc. In most I I I I I

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2I cases, a high density material is desired because it helps to ensure that the fuel element will burn long enough to simulate the burning time of a conventional cigarette and that it will provide sufficient energy to generate the required amount of aerosol.

The fuel elements employed herein are advantageously molded or extruded from comminuted tobacco, reconstituted tobacco, or tobacco substitute materials, such as modified cellulosic materials, degraded or prepyrolyzed tobacco, and the like. Suitable materials include those described in U.S. Patent No. 4,347,855 to Lanzilotti et al., U.S. Patent No. 3,931,824 to Miano et al., and U,S, Patent Nos. 3,885,574 and 4,008,723 to Borthwick et al. and in Sittig, Tobacco Substitutes, Noyes Data Corp. (1976). Other suitable combustible materials may be employed, as long as they burn long enough to simulate the burning time of a conventional cigarette and generate sufficient heat for the aerosol generating means to produce the desired level of aerosol from the aerosol forming material.

Preferred fuel elements normally include combustible carbon material,;, such as those obtained by the pyrolysis or carbonization of cellulosic materials, such as wood, cotton, rayon, tobacco, coconut, paper, and the like. In most cases, combustible carbon is desirable because of its high heat generating capacity and because it produces only minimal amounts of incomplete combustion products. Preferably, the carbon content of the fuel element is about 20 to 40% by 30 weight, or more, The most preferred fuel elements useful in practicing this invention are carbonaceous fuel elements fuel elements primarily comprising carbon), which are described and claimed in copending -0 0(M, rild gplul. 1t, 4 tt It I I It it i 4 II 01 4 14 4 I r f L t II f I I' i i Y~ll~llly~ 11411-.

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Carbonaceous fuel elements are particularly advantageous because they produce minimal pyrolysis and incomplete combustion products, produce little or no visible sidestream smoke, and minimal ash, and have high heat capacity. In especially preferred embodiments, the aerosol delivered to the user has no significant mutagenic activity as measured by the Ames test. See Ames et al., Mut. Res., 31:347-364 (1975); Nagas et al., Mut. Res., 42:335 (1977).

Burn additives or combustion modifying agents also may be incorporated in.o the fuel to provide the appropriate burning and glow characteristics. If desired, fillers, such as diatomaceous earth, and binders, such as sodium carboxymethyl cellulose (SCMC), also may be incorporated into the fuel. Flavorants, such as tobacco extracts, may be incorporated into the fuel to add a tobacco or ether flavor to the aerosol.

Preferably, the fuel element is provided with 20 one or more longitudinally extending passageways.

These passageways help to control transfer of heat from the fuel element to the aerosol generating means, which is important both in terms of transferring enough heat to produce sufficient aerosol and in terms of avoiding 25 the transfer of so much heat that the aerosol former is degraded. Generally, these passageways provide porosity and increase early heat transfer to the substrate by increasing the amount of hot gases which reach the substrate, They also tend to increase the 30 rate of burning.

Generally, a large number of passageways, about 5 to 9 or more, especially with a relatively wide spacing between the passageways, as in Figures 1A, 7A, and 9A, produce high convective heat transfer, which leads to high aerosol delivery. A

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4 tt t 4 .44 4 44 4 4 *d 1 4, t I #4 -:ii r large number of passageways also generally helps assure ease of lighting.

High convective heat transfer tends to produce a higher CO output in the mainstream. To reduce CO levels, fewer passageways or a higher density fuel element may be employed, but such changes generally tend to make the fuel element more difficult to ignite, and to decrease the convective heat transfer, thereby lowering the aerosol delivery rate and amount.

However, it has been discovered that with passageway arrangements which are closely spaced, as in Figure 7B, such that they burn out or coalesce to form one passageway, at leasz at the lighting end, the amount of CO in the combustion products is generally lower than in the same, but widely spaced, passageway arrangement.

The optimum arrangement, configuration, and number of fuel element passageways should delivery a steady and high supply of aerosol, allow for easy S ignition, and produce low CO. Various combinations have been examined for passageway arrangement/con- Sfiguration and/or number in carbonaceous fuel elements used in various embodirents of the invention. In general, it hs been discovered that fuel elements S: having from about 5 to 9 passageways, relatively closely spaced such that they burn away into one large passageway, at least at the lighting end of the fuel element, appear to most closely satisfy the requirements of a preferred fuel element for use in this invention, especially for the preferred carbonaceous E 30 fuel elements. However, it is believed that this Sphenomenon also occurs with the various noncarbonaceous fuel elements which may be employed in practicing the invention, Variables which affect the rate at which the fueal element passageways will coalesce upon burning _T i i-i-~ include the density and composition of the fuel element, the size, shape, and number of passageways, the distance between the passageways, and the arrangement thereof. For example, for a 0.85 g/cc carbonaceous fuel source having seven passageways of about mm, the passageways should be located within a core diameter, the diameter of the smallest circle which will circumscribe the outer edge of the passageways, between about 1.6 mm and 2.5 mm in order for them to coalesce into a single passageway during burning.

However, when the diameter of the seven passageways is increased to about 0.6 mm, the core diameter which will coalesce during burning increases to about 2.1 mm to about 3,0 mm.

Another preferred fuel element passageway arrangement useful in embodiments of the invention is the configuration illustrated in Figure 9B, which has been found to be particularly advantageous for low CO delivery and ease of lighting. In this preferred 20 arrangement, a shrt section at the lighting end of the fuel element is provided with a plurality of passages, preferably from about 5 to 9, which merge into a large cavity 97 which extends to the mouth end of the fuel element. The plurality of passages at the lighting end 25 provide the large surface area desired for ease of lighti.ng and early aerosol delivery. The cavity, which may be from about 30% to 95%, preferably more than of the length of the fuel element, helps assure uniform heat transfer to the aerosol generating means and tends 30 to delivery low CO to the mainstream.

The aerosol generating means used in practicing the invention is physically separate from the fuel element. By physically separate it is meant that the substrate, container, or chamber which contains the aerosol forming materials is not mixed with, or a part i j i

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r cr *i 4i 44*1 4 9,4 4r 4 Ii 4, 4 I I ;t I 44 4 It 44 I ct f I II~ I~" of, the burning fuel element. As noted previously, this arrangement helps reduce or eliminate thermal degradation of the aerosol forming material and the presence of sidestream smoke. While not a part of the fuel, the aerosol generating means is preferably in a conductive heat exchange relationship with the fuel element, and preferably abuts or is adjacent to the fuel element. More preferably, the conductive heat exchange relationship is achieved by a heat conducting member, such as a metal tube or foil, which is preferably recessed or spaced from the lighting end of the fuel.

Preferably, the aerosol generating means includes one or more thermally stable materials which carry one or more aerosol forming materials. As used herein, a thermally stable material is one capable of withstanding the high temperatures, 400 0 C-600 0

C,

which exist near the fuel without decomposition or burning. While not preferred, other aerosol generating 20 means, such as heat rupturable microcapsules, or solid rte aerosol forming substances, are within the scope of the invention, provided they are capable of releasing sufficient aerosol forming vapors to satisfactorily resemble tobacco smoke.

Thermally stable materials which may be used as a substrate or carrier for the aerosol forming materials are well known to those skilled in the art.

Useful substrates should be porous and must be capable f *of retaining an aerosol forming material when not in 30 use and capable of releasing a potential aerosol forming vapor upon heating by the fuel element. Substrates, especially partic'ilates, may be placed within a container, preferably formed from a conductive material.

Useful thermally stable materials include thermally stable adsorbent carbons, such as porous

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ij grade carbons, graphite, activated, or nonactivated carbons, and the like. Other suitable materials include inorganic solids such as ceramics, glass, alumina, vermiculie, clays such as bentonite, and the I 5 like. Preferred carbon substrate materials include porous carbons such as PC-25 and PG-60 available from Union Carbide, and SGL carbon available from Calgon. A Spreferred alumina substrate is SMR-14-1896, available from the Davidson Chemical Division of W.R. Grace 1 10 Co., which is sintered at elevated temperatures, e.g., greater than about 1000 0 C, washed, and dried prior to use.

It has been found that suitable particulate substrates also may be formed from carbon, tobacco, or mixtures of carbon and tobacco, into densified particles in a one-step process using a machine made by Fuji Paudal KK of Japan, and sold under the trade name of "Marumerizer", This apparatus is described in German Patent No. 1,294,351 and U.S. Patent No.

i 2 20 3,277,520 (now reissued as No. 27,214) as well as Japanese published specification No. 8664/1967.

ITI he aerosol generating means used in the invention is advantageously spaced no more than about mm, preferably no more than 30 mm, most preferably *25 no more than 20 mm from the lighting end of the fuel element. The aerosol generator may vary in length from about 2 mm to about 60 mm, preferably from about 5 mm tiff tto 40 mm, and most preferably from about 20 mm to mm, The diameter of the aerosol generating means may S. 30 vary from about 2 mm to about 8 mm, preferably from Sabout 3 to 6 mm. If a non-particulate substrate is J used, it may be provided with one or more holes, to increase the surface area of the substrate, and to increase air flow and heat transfer.

r- The aerosol forming material or materials uved in the invention must be capable of forming an aerosol at the temperatures present in the aerosol generating means when heated by the burning fuel element. Such materials preferably will be composed of carbon, hydrogen and oxygen, but they may include other materials. The aerosol forming materials can be in solid, semisolid, or liquid form. The boiling point of the material and/or the mixture of materials can range up to about 500 C. Substances having these characteristics include polyhydric alcohols, such as glycerin and propylene glycol, as well as aliphatic esters of mono-, di-, or poly-carboxylic acids, such as methyl stearate, dodecandioate, dimethyl tetradodecandioate, and others.

The preferred aerosol forming materials are polyhydric alcohols, or mixtures of polyhydric alcohols. Especially preferred aerosol formers are glycerin, propylene glycol, triethylene glycol, or mixtures thereof.

The aerosol forming material may be dispersed on or within the aerosol generating means in a concentration sufflcient to permeate or coat the substrate, carrier, or container, For example, the aerosol forming substance may be applied full strength or in a dilute solution by dipping, spraying, vapor deposition, or similar techniques, Solid aerosol forming components may be admixed with the substrate and distributed evenly throughout prior to formation.

While the loading of the atrosol forming material will vary from carrier to carrier and from aerosol forming material to aerosol forming material, the amount of liquid aerosol forming materials may generally vary from about 20 mg to about 120 mg, preferably from about 35 mg to about 85 mg, and most preferably from about 45 mg to about 65 mg. As much as possible of the aerosol former carried on the aerosol generating means should be delivered to the user as WTPM. Preferably, above about 2 weight percent, more preferably above about 15 weight percent, and most preferably above about 20 weight percent of the aerosol former carried on the aerosol generating means is delivered to the user as WTPM.

The aerosol generating means also may include one or more volatile flavoring agents, such as menthol, vanillin, artificial coffee, tobacco extracts, nicotine, caffeine, liquors, and other agents which impart flavor to the aerosol, It also may include any other desirable volatile solid or liquid materials. Alternatively, these optional agents may be placed between the aerosol generating means and the mouthend, such as in a separate substrate or chamber in the passage which leads from the aerosol generating means to the mouthend, or in the optional tobacco charge, If desired, 4 20 these volatile agents may be used in lieu of part, or all, of the aerosol forming material, so that the article delivery a nonaerosol flavor or other material to the user.

One particularly preferred aerosol generating i 25 means comprises the aforesaid alumina substrate containing spray dried tobacco extract, tobacco flavor it modifiers, such as levulinic acid, one or more flavoring agents, and an aerosol forming material, such as glycerin. Th s substrate may be mixed with densified tobacco particles, such as those produced on a "Marumerizer" which particles also may be impregnated A, with an aerosol forming material.

Articles of the type disclosed herein may- be used, or may be modified for use, as drug delivery articles, for delivery of volatile pharmacologically or I I Il physiologically active materials such as ephedrine, metacroterenol, terbutaline or the like.

As shown in the illustrated embodiments, the smoking article of the present invention also may include a charge or plug of tobacco or a tobacco containing material downstream from the fuel element, which may be used to add a tobacco flavor to the aerosol. In such cases, hot vapors are swept through the tobacco to extract and vaporize the volatile components in the tobacco, without combustion or substantial pyrclysis. One preferred location for the tobacco charge is around the periphery of the aerosol generating means, as showen in Fgures 8 and 9, which increases heat transfer to the tobacco, especially in embodiments which employ a heat conducting member or conductive container between the aeroscl forming material and the peripheral tchaccc jacket. The tobacco in these embodiments also acts as an insulating member for the aerosol genera r and helps simulate the feel and aroma of a crnentional cigarette. Another preferred location fc the tobacco charge is within the aerosol generating means, where tobacco or densified tobacco particles ma:. be m:*xed with, or used in lieu of, the substrate for the aerosol forming materials.

The tobacco cntanag material may contain any tobacco available to the skilled artisan, such as Burley, Flue Cured, Turkish, reconstituted tobacco, extruded or dens.fied tobacco mixtures, tobacco containing sheets and the like, Advantageously, a blend of tobaccos may be used to contribute a greater variety of flavors., The tobacco containing material may also include conventional tobacco additives, such as fillers, casings, reinforcing agents, such as glass fibers, humectants, and the like. Flavor agents may I AN U-C

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1 i,, .1, likewise be added to the tobaco material, as well as flavor modifying agents.

The heat conducting member preferably employed in practicing this invention is typically a metallic aluminum) tube, strip, or foil varying in thickness from less than about 0.01 mm to about 0.2 mm or more. The thickness, shape, and/or type of conducting material other metals or Grafoil from Union Carbide) may be varied to achieve virtually any desired degree of heat transfer, In general, the heat conducting member should be sufficiently recessed to avoid any interference with the lighting of the fuel element, but close unough to the lighting end to provide conductive heat transfer on the early and middle puffs, As shown in the illustrated embodiments, the heat conducting member preferably contacts or overlaps the rear portion cf the fuel element and at least a portion of the aerosce generating means and is recessed 20 or spaced from the lighting end, by at least about 3 mm or more, preferably by about 5 mm or mcre, Preferably, the heat cond tt' member extends over no more than about one-half the length of the fuel element. More preferably, the heat conducting member overlaps or otherwise contacts no more than about the rear 5 mm of the fuel element. Preferred recessed members of this type do not interfere with the lighting or burning of the fuel element, preferred recessed conducting members also help to extinguish the fuel when it burns 30 back to the point of contact by the conductor, by acting as a heat sink, and do not protrude, even after the fuel has been consumed.

Preferably, the heat conducting member also forms a conductive container which encloses the aerosol forming materials. Alternatively, a separate conductive, tt AI t

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container may be provided, especially in embodiments which employ particulate substrates or semi-liquid aerosol forming materials. In addition to acting as a container for the aerosol forming materials, the conductive container improves heat distribution to the aerosol forming materials and the preferred peripheral tobacco jacket and helps to prevent migration of the aerosol former to other components of the article, The container also provides a means for controlling the pressure drop through the article, by varying the number, size, and, or position of the passageways through which the aerosol former is delivered to the moutbend .ece of the article, M'oreover, in embodments with a tobacco jacket around the periphery of the aerosol generating means, the container may be provided with peripheral passages or slots to control and direct the flow of vapors through the tobacco. The use of a container also simplifies the manufacture of the article by reducing the number of necessary elements and/or manufacturing steps, ,The insulatlng member- which may be employed in pra-cticin the invention are preferably formed into a resiient jacket from one or more layers of an insul a-ng material Advantageously, this jacket is at least 0.5 m. thick, preferably at least I. mm thick, and more preferably from about 1,5 to about 2 mm thick, Preferably, the jacket ex;ends over more than half the length of the fuel element. More preferably, it extends over substantially the entire outer periphery of the fuel element and all or a portion of the aerosol generating means, As shown in the embodiment of Figure 8, different materials may be used. to insulate these two components of the article, Insulating members which may be used in accordance with the present invention generally

I

comprise inorganic or organic fibers such as 'those made out of glass, alumina, silica, vitreous materials, mineral wool, carbons, silicons, boron, organic polymerr. celluJlosics, and the like, including mixtures cf thes-e materials, Nonfibrous, insulating materials, such as silica aerogel, pearlite, glass, and the like, formed in mats, strips or other shapes, may also be used. Preferred insulating members are resilient, to help simulate the feel of a conventional cigarette.

Preferred insuiaz,.c materials should fuse during use and should have a softening temperature below about 650-700C0C. Preferred insulating materials also should not, burn during use, However, slow burn~ng carbons and like mazerials may be employed, These materials act primarily as an insulating jacket, retaining and directing a Eign:. fcant portion of the heat formed by the burn,4ng fuel element to the aerosol generatin~g means. Beca-u e the nsu'a4.ng jacket becomes hot adJacent to the burning fuel element, to a limited 20 exten~t, It alsc may condu,,ct heat toward the aerosol g en e ra t-n rns Currently preferred insulating materials for the fuel element include ceramic fibers, such as glass fibers, Two suitable gl ass fibers are available from the Mannling Paper Company of Troy, New York, Under the designa.t~ios t'anniqlau 1000 and Manrniglas 12001 Preferred cj2afs fiber materials have a low softening point, below about 650 0Co Using PSTM test method C 3:3 -13, Pref~erred qlazs fibers include ex~perimental.

30 materials produced by Owens-Corning of Toledo, Ohio under the dlesignations 6432 and 6437, which have a soft~ening point of about 640 0 C and fuse during use, Several commercially available inorganic 4ib~erz are p~repared with a binder, PVA, which acts to maintain struav,,ral integrity during handling, It

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oM~raraaa~~ These binders, which would exhibit a harsh aroma upon heating, should be removed, by heating in air at about 650°C for up to about 15 min. before use. If desired, pectin, at about 3 wt. percent, may be added to the fibers to provide mechanical strength to the jacket without contributing harsh aromas.

Alternatively, the insulating material may be replaced, in whole or in part, by tobacco, either loosely packed or tightly packed. The use of tobacco as a substitute for part or all of the insulating jacket serves an additional function by adding tobacco flavors to the mainstream aerosol and producing a tobacco sidestream aroma, in addition to acting as an i:sulator. In preferred embodiments where the tobacco jacket encompasses the aerosol generating means, the jacket acts as a non-burning insulator, as well as contributing tobacco flavors to the mainstream aerosol.

In embodiments where the tobacco encircles the fuel, the tobacco is preferably consumed only to the extent 20 that the fuel source is consumed, up to about the point of contact between the fuel element and the

'I

aerosol, generating means, This may be achieved by compressing the tobacco around the fuel element and/or I using a conductive heat sink, as in the embodiment of Figure 9, It also may be achieved by treating the cigarette paper overwrap and/or thi tobacco with materials which help extinguish the tobacco at the point where it overlaps the aerosol generating means.

When the insulating member comprises fibrous materials other than tobacco, there may be employed a barrier means between the insulating member and the mouth end of the article. One such barrier means comprises at, annular member of high density cellulose acetate tow which abuts the fibrous insulating means 1 and which is sealed, at either end, with, for example, glue, to block air flow through the tow.

In most embodiments of the invention, the fuel/aerosol generating means combination will be attached to a mouthend piece, such as a foil lined paper or cellulose acetate/plastic tubes illustrated in the Figures, although a mouthend piece may be provided separately, in the form of a cigarette holder.

This element of the article provides the passageway which channels the vaporized aerosol forming materials into the mouth of the user. Due to its length, preferably about 35 to 50 mm or more, it also keeps the hoc fire cone away from the mouth and fingers of the user and provides sufficient time for the hot aerosol to form and cool before it reaches the user.

Suitable mouthend pieces should be inert with respect to the aerosol forming substances, may have a wcter or liquid proof inner layer, should offer minimum -o aerosol loss by condensation or filtration, and should be capable of withstanding the temperature at the interface with the other elements of the article.

Preferred mouthend pieces include the cellulose-acetate tube employed in many of the illustrated embodiments which acts as a resilient outer member and helps simulate the feel of a conventional cigarette in the mouth end portion of the article. Other suitable mouthend pieces will be apparent to those of ordinary skill in the art.

Meuthend pieces useful in articles of the invention may include an optional "filter" tip, which is used to give the article the appearance of the conventional filtered cigarette, Such filters include low efficiency cellulose acetate filters and hollow-or baffled plastic filters, such as those made of poly,- A0 re i I_ -I c ~j I. 5 propylene. Such filters do not appreciably interfere with aerosol delivery.

The entire length of article or any portion thereof may be overwrapped with cigarette paper.

Preferred papers at the fuel elem ent end should not openly flame during burning of the fuel element. In addition, the paper should have controllable smolder properties and should produce a grey, cigarette-like ash.

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C r In those embodiments utilizing an insulating jacket wherein the paper burns away from the jacketed fuel element, maximum heat transfer is achieved because air flow to the fuel source is not restricted.

However, papers can be designed to remain wholly or partially intact upon exposure to heat from the burning fuel element. Such papers provide restricted air flow to the burning fuel element, thereby helping to control the temperature at which the fuel element burns and the subsequent heat transfer to the aerosol generating 20 means.

Tc reduce the burning rate and temperature of the fuel element, thereby maintaining a low CO/CO 2 ratio, a non-porous or zero-porosity paper treated to be slightly pcrous, e non-combustible mica paper with a plurality of holes therein, may be employed as the overwrap layer. Such a paper controls heat delivery, especially in the middle puffs puffs 4 through 6).

To maximize aerosol delivery which otherwise would be diluted by radial outside) air infiltration through the article, a non-porous paper may be used from the aerosol generating means to the mouth end.

Papers such as these are known in the cigarette paper art and combinations of such papers may 41

P

i I be employed to produce various functional effects.

Preferred papers used in the articles of the present invention include Ecusta 01788 and 646 plug wrap manufactured by Ecusta of Pisgah Forest, North Carolina, and Kimberly-Clark's KC-63-5, P 878-5, P 878-16-2, and 780-63-5 papers.

Preferred embodiments of the invention are capable of delivering at least 0.6 mg of aerosol, measured as wet total particulate matter (WTPM), in the first 3 puffs, when smoked under FTC smoking conditions. (FTC smoking conditions consist of two seconds of puffing (35 ml total volume) separated by 58 seconds of smolder.) More preferred embodiments of the invention are capable of delivering 1.5 mg or more of aerosol in the first 3 puffs. Most preferably, embodiments of the invention are capable of delivering 3 mg or more of aerosol in the first 3 puffs when smoked under FTC smoking conditions. Moreover, preferred embodiments of the invention deliver an average of at least about 0.8 mg of wez total particulate matter per puff for at least about 6 puffs, preferably for at least about 1C puffs, under FTC smoking conditions.

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Claims (1)

1. 32- The claims defining the inventio. are as follows: 1. A cigarette-type smoking article comprising a carbonaceous fuel element and a physically separate aerosol generating means including an aerosol forming material, the aerosol generating means being located between the fuel element and the mouthend of the article and further comprising a physically separate tobacco containing mass circumscribing at least a portion of the aerosol generating means. 2. A cigarette type smoking article comprising a combustible fuel element having a length of less than 30 mm.; a physically separate aerosol generating means including an aerosol forming material, the physically separate aerosol generating means being located between the fuel element and the mouthend of the article; and further comprising a physically separate tobacco containing mass circumscribing at least a portion of the S, aerosol generating means, 3. The smoking article of Claims 1 or 2 additionally comprising a heat conductive element which encloses the aerosol forming material and t which is circumscribed by the separate tobacco containing mass. 4. The smoking article of Claim 3 wherein the heat conductive i S* element contacts the fuel element. The smoking article of any one of Claims 1 to 4 additionally comprising a non-burning Insulating member which circumscribes all or a portion of the fuel element. 6. The smoking article of any one of Claims 1 to 5 wherein the end of the separate tobacco containing mass nearest the lighting end of the fuel element is located less than 30 mm. from the lighting end of the smoking article. The smoking article of any one of Claims I to 6 further comprising a mouthend piece. S8, The smoking article of any one of Claims 1 to 7 wherein the fuel element comprises a plurality of longitudinal passages. I A0- 9. The smoking article of Claim 8 wherein the non-burning Insulating member which circumscribes the fuel element is resilient and at least 0.5 mm, In thickness. A smoking article comprising a combustible fuel element and a physically separate aerosol generating means including an aerosol forming material, the fuel element including a plurality of longitudinal passageways which are arranged such that during burning they coalesce Into a single passageway at least at the lighting end of the fuel element. KLN/1371b I i~1 i 33 11. The smoking article of Claim 10 wherein the fuel element Is carbonaceous. 12. The smoking article of Claims 10 or 11 wherein the fuel element has a length of less than 30 mm. 13. The smoking article of any one of Claims 10 to wherein the fuel element has a length of less than 20 mm. 14. The smoking article of any one of Claims 1 to 13 wherein there are at least five longitudinal passageways through said fuel element prior to burning. The smoking article of any one of Claims 10-14 wherein the fuel element and the physically separate aerosol generating means are arranged in a conductive heat exchange relationship such that the aerosol generating means receives conductive heat substantially throughout the time of burning of the fuel element. 16. The smoking article of any one of Claims 10 to 15 wherein the fuel element has at least seven longitudinal passageways extending therethrough. t 0 17. The smoking article of any one of Claims 10 to 16 wherein the fuel element has at least nine longitudinal passageways extending therethrough. DATED this ELEVENTH day of SEPTEMBER 1989 R. J. REYNOLDS TOBACCO COMPANY Patent Attorneys for the Applicant SPRUSON FERGUSON rri tf.c r 6-- KLN '/1371 b