NO166566B - ROEKEARTIKKEL. - 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

The present invention relates to a smoking article of the cigarette type, which produces an aerosol that resembles tobacco smoke, and which advantageously contains, in quantities that are incomplete, combustion and pyrolysis products compared to those normally produced by a conventional cigarette.

Many smoking articles have been proposed over the years, particularly in the last 20 to 30 years, but none of these products have ever achieved any commercial success.

Despite decades of interest and effort, there is still no smoking article on the market that provides the benefits associated with conventional cigarette smoking, without providing the significant amounts of incomplete combustion and pyrolysis products generated by a conventional cigarette.

The invention comprises a cigarette-type smoking article comprising a carbonaceous fuel element in the ignition end of the cigarette and a physically separate aerosol generating agent located between the fuel element and the mouth end of the article. A ring of tobacco-containing material surrounds at least a portion of the aerosol-generating means. Preferably, the smoking article comprises a heat-conducting element arranged to conduct heat from the fuel element to the aerosol-generating means. It is also preferred that the fuel element comprises a or

several longitudinal passageways. It is advantageous that at least part of the fuel element is surrounded by an elastic, insulating jacket to reduce radial heat loss. Upon ignition, the fuel element generates heat which is used to vaporize the aerosol-forming materials in the aerosol-generating agent. These materials are then drawn towards the mouth end, especially during suction, and into the user's mouth, similar to the smoke in a conventional cigarette.

The smoking articles according to the invention are capable of producing significant amounts of aerosol, both initially and during the product's lifetime, and can give the user the same pleasures as cigarette smoking. The aerosol produced by the aerosol-generating agent is produced without significant heat breakdown and is advantageously delivered to the user with substantially reduced amounts of pyrolysis and incomplete combustion products than is normally delivered by a conventional cigarette.

The annular portion of tobacco-containing material placed around the perimeter of the aerosol-generating means helps to stimulate the feel and aroma of a conventional cigarette. When the fuel element burns, hot gases are passed advantageously through the material containing tobacco, so that the smoke-like aerosol includes the volatile tobacco aroma and taste.

It is advantageous that the small fuel element used in smoking articles according to; invention has a length of less than approx. 30 mm, preferably less than approx. 20 mm, and has a density of at least approx. 0.5 g/cm<3>, more preferably at least approx. 0.7 g/cm<3>, measured e.g. by means of mercury displacement. Suitable fuel elements can be cast or extruded from split or reconstituted tobacco and/or a tobacco substitute and preferably contain combustible carbon. Preferred fuel elements are also provided with one or more longitudinal passageways, more preferably from 5 to 9 passageways or more, which help regulate heat transfer from the burning fuel element to the aerosol-forming material in the aerosol-generating agent.

The aerosol-generating agent advantageously comprises a substrate or a carrier, preferably of a heat-stable material, which carries one or more aerosol-forming materials. There is preferably a conductive heat exchanger relationship between the fuel element and the aerosol generator. The conductive heat exchanger ratio between the fuel and the aerosol generator is preferably achieved by providing a heat conductive part, such as e.g. a metal conductor, which is in contact with the fuel element and the aerosol generating agent and effectively conducts or transfers heat from the burning fuel element to the aerosol generating agent. This heat conducting part preferably contacts the fuel element and the aerosol generating means around at least part of their peripheral surfaces and is preferably set back from or at a distance from the igniting end of the fuel element, advantageously by at least 3 mm, preferably by at least 5 mm, for to avoid interference with ignition and burning of the fuel and to avoid any protrusion of the heat-conducting part. Most preferably, the heat-conducting part also encloses at least part of the substrate for the aerosol-forming materials. Alternatively, a separate conductive container may be used to contain the aerosol-forming materials.

At least part of the aerosol-generating means is provided with a peripheral sheath of the material containing tobacco, such as tobacco or tobacco mixed with insulating fibers, for example glass fibers. The annular portion of tobacco placed around the peripheral portion of the aerosol generating means advantageously functions as an insulating portion to help retain heat within the aerosol generating means. The ring-shaped tobacco also helps to simulate the aroma, feel and taste of a conventional cigarette.

Preferably, at least one part of the fuel element is equipped with a peripheral insulating part, which e.g. a sheath of insulating fibers. This part reduces radial heat loss and helps to retain and direct heat from the fuel element to the aerosol generating agent and to reduce the incendiary property of the fuel. The material used to insulate the fuel element may be the same tobacco-containing material that surrounds the aerosol generating means, or it may be another material such as a jacket consisting entirely of insulating fibers such as glass fibers.

Because the preferred fuel element is relatively short, the hot burning cone is always close to the aerosol generating means, maximizing heat transfer thereto and the resulting production of aerosol, particularly in embodiments equipped with a fuel element with multiple passages through the fuel element, a thermally conductive part and/or an insulating part. A relatively high density fuel material is used to help ensure that the small 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 desired amounts of aerosol. Because the aerosol-forming substance is physically separated from the fuel element, it is exposed to significantly lower temperatures than those present in the burning cone, thereby reducing the possibility of thermal degradation of the aerosol generator.

The smoking article according to the present invention is normally equipped with a mouthpiece including means, such as e.g. a longitudinal passage, for delivery of the volatile materials produced by the aerosol generating means to the user. Preferably, the mouthpiece comprises an elastic outer part, which e.g. an annular section of cellulose acetate, to help simulate the feel of a conventional cigarette. The article advantageously has the same overall dimensions as a conventional cigarette, and as a result, the mouthpiece and aerosol delivery means typically span approx. half or more of the length of the article. Alternatively, the fuel element and aerosol generating means may be manufactured without an integral nozzle or aerosol delivery means, for use with a separate, disposable or reusable nozzle.

A tobacco charge may be placed between the article's aerosol generating means and the mouthpiece. A tobacco batch can also be mixed with, or used as, a substrate for the aerosol-forming material. Other substances, such as flavourings, can also be mixed into the article to flavor or otherwise modify the aerosol delivered to the user.

Smoking articles according to the present invention normally use substantially less fuel on a volume basis, and preferably on a weight basis, than conventional cigarettes to produce acceptable aerosol levels. The aerosol delivered to the user also normally has less pyrolysis and incomplete combustion products, due to the undecomposed aerosol from the aerosol-generating agent and because the short, high-density fuel element, especially in embodiments with multiple longitudinal passages, produces substantially reduced amounts of pyrolysis and/or incomplete combustion products compared to a conventional cigarette, even when the fuel element comprises tobacco or other cellulosic materials.

As used herein, and only for the purposes of the present application, "aerosol" is defined to include vapors,

gases, particles and the like, both visible and invisible, and especially those constituents perceived by the user as being "smoke-like", generated by the action of the heat of the burning fuel element on substances contained in the aerosol-generating agent, or otherwise in the article . Defined in this way, the term "aerosol" also includes volatile flavoring agents and/or pharmacologically or physiologically active agents, regardless of whether they produce a visible aerosol.

As used herein, the term "conductive heat exchanger arrangement" is defined as a physical arrangement of the aerosol-generating agent and the fuel element whereby heat is transferred by conduction from the burning fuel element to the aerosol-generating agent during substantially the entire burning period of the fuel element. Conductive heat exchange conditions can be achieved by placing the aerosol-generating means in contact with the fuel element and in close proximity to the burning part of the fuel element, and/or by using a conductive part to transfer heat from the burning fuel to the aerosol-generating means.

As used herein, the term "insulating part" refers to

all materials that primarily act as insulators. These materials preferably do not burn during use, but they may include slow-burning carbons and similar materials, and especially materials which melt during use, such as e.g. glass fibers that melt at low temperature. Suitable insulators have a thermal conductivity in g-cal/(sec) (cm<2>)(°C/cm), of less than approx. 0.05, preferably less than approx. 0.02, most preferably less than approx. 0.005.

The smoking article according to the present invention is described in more detail in the accompanying drawings and in the detailed description of the invention that follows. Figures 1, 2 and 3 show longitudinal cross-sections of different embodiments of the invention. Figs. IA, IB, 1C and 3A are end cross-sections showing various configurations of fuel element passages suitable for use in embodiments of the invention, Fig. 2A is a cross-section of the embodiment of Fig. 2 taken

along lines 2A-2A in fig. 2,

Fig. 2B shows an enlarged image of the end of that metal container used in the embodiment in fig. 2, and Fig. 3B is a longitudinal cross-section of a preferred configuration of a fuel element passage suitable for use in embodiments of the invention.

The embodiments of the invention illustrated in figures 1, 2 and 3 preferably have overall dimensions like a conventional cigarette. As shown, each of the smoking articles includes a card, approx. 20 mm long, combustible fuel element 10, and an adjacent aerosol generating means 12.

In the embodiment of fig. 1, an elastic, insulating glass fiber sheath 72 surrounds the periphery of both the fuel element 10 and the aerosol generating agent 12. It is advantageous if the elastic sheath 72 is composed of a mixture of tobacco and insulating fibers, such as e.g. glass fibers. It is advantageous if the glass fibers melt when the fuel element burns.

This sheath 72 is wrapped in a non-porous paper 73, which e.g. "P 878-5" available from Kimberly-Clark Corporation. In this embodiment, the fuel element is approx. 15 to 20 mm long and is preferably equipped with three or more holes 16 to increase the airflow through the fuel. Three suitable passage arrangements are illustrated in figures IA, IB and 1C.

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

A plastic tube 44 abuts or preferably overlaps the end wall 78 of the metal container 74 and is surrounded by a section of a resilient, high-density cellulose acetate rope 42. An adhesive layer 82 or other material may be applied to the fuel end of the rope 42 to seal the rope and block airflow through it. . A low efficiency filter plug 45 is placed on the mouth end of the article and the rope 42 and the filter plug 45 is preferably wrapped in a conventional plug wrapping paper 85. Another cigarette paper layer 86 may be used to connect the rear end of the insulating sheath 72 and the rope/filter section.

In a modified version of the embodiment of fig. 1, the tobacco/glass fiber sheath 72 may also be used in place of the cellulose acetate rope 42, so that the sheath extends from the ignition end to the filter plug 45. In embodiments of this type, an adhesive layer is applied to the annular section of the filter plug that abuts the end of the insulating sheath, or a short, annular section of a rope is placed between the insulating jacket and the filter piece, glue being applied to both ends.

Fig. 2 illustrates an embodiment in which a 10 to 15 mm long fuel element 10 is surrounded by an insulating jacket

72 of glass fibers and the aerosol-generating agent is surrounded by a sheath of tobacco 88. The glass fibers used in this embodiment preferably have a softening temperature below approx. 650°C, such as test fibers 6432 and 6437 obtained from Owens-Corning, Toledo, Ohio, so that they will melt during use. The glass fiber and tobacco covers are both encased in a plug sleeve 85, which e.g. Ecusta 646, and is connected with an overwrap of cigarette paper 89, which e.g. 780-63-5 or P 878-16-2, obtained from Kimberly-Clark. In this embodiment, the metal cap 90 overlaps the rear 3-4 mm of the fuel element so that it has a distance of approx. 6 - 12 mm from the ignition end, and the rear part of the capsule 90 is crimped into a tab shape, as shown in fig. 2B. A passage 91 is placed at the mouth end of the capsule,

in the center of the capsule. Four additional passages 92 are provided at the transfer points between the shrunk and unshrunk portions of the capsule. Alternatively, the rear part of the capsule may have a rectangular or square cross-section instead of the tabs, or a simple tubular capsule with a crimped mouth end, with or without peripheral passages 92, may be used.

At the mouth end of the tobacco sheath 88 is a mouthpiece 40 comprising an annular section of cellulose acetate rope 42, a plastic tube 44, a low efficiency filter piece 45 and layers of cigarette paper 85 and 89. The mouthpiece 40 is connected to the sheathed fuel/capsule end with a surrounding layer of paper 86.

As illustrated, the capsule end of the plastic tube 44 has a distance from the capsule 90. The hot vapors flowing through the passages 90 thus pass through the tobacco sheath 88, where volatile components in the tobacco are vaporized or extracted, and then in passage 18 where the tobacco sheath molds against the cellulose acetate rope 42.

In embodiments of this type with an insulating sheath 72 of low-density fuel, some air and gases pass through the sheath 72 and into the tobacco sheath 88. Thus, the peripheral passage 92 in the capsule need not be necessary to extract tobacco flavor from the tobacco sheath 88. In the embodiment of fig. 3, the cover 94 comprises tobacco or a mixture of tobacco and insulating fibres, such as e.g. glass fibers. As shown, the tobacco cap 94 extends just beyond the mouth end of the metal container 96. Alternatively, it may extend the entire length of the article, up to the filter piece at the mouth end. In embodiments of this type, the container 96 is preferably provided with one or more longitudinal slits 99 on its periphery (preferably two slits 180° apart) so that vapors from the aerosol generator pass through the annular section of tobacco surrounding the aerosol generator to extract tobacco flavor before they enters passage 18.

As illustrated, the tobacco is compressed with the fuel element end of the jacket 94. This helps reduce airflow through the tobacco, thereby reducing its burning potential.

In addition, the container 96 helps extinguish the tobacco wood

to act as a heat sink. This heat sink effect helps to extinguish any burning of the tobacco surrounding the capsule, and it also helps to distribute heat evenly to the tobacco around the aerosol generating means, thereby aiding in the release of tobacco flavoring constituents. In addition, it may be desirable to treat it. the part of the cigarette paper wrapper 85, 89 near the rear end of the fuel with a material, such as sodium silicate, to help extinguish the tobacco so that it will not burn significantly beyond the exposed portion of the fuel element. Alternatively, the tobacco itself can be treated with a burning modifier to prevent the tobacco surrounding the aerosol generator from burning.

Upon ignition of any of the aforementioned embodiments, the fuel element burns, generating the heat used to volatilize the aerosol-forming material or materials present in the aerosol-generating agent. These volatile materials are then drawn towards the mouth end, especially by sucking, and into the user's mouth, in the same way as the smoke in a conventional cigarette.

Because the fuel element is relatively short, the hot, burning cone of fire is always close to the aerosol generating body, maximizing heat transfer to the aerosol generating agent and any tobacco charges, and the resulting production of aerosol and any tobacco flavoring, especially when the preferred heat conducting part is used . Because the fuel element is short, there is never a long section of non-burning fuel to act as a heat sink, as was common in earlier thermal aerosol articles. The small fuel source also tends to reduce the amount of incomplete combustion or pyrolysis products, especially in embodiments containing carbon and/or multiple passages.

Heat transfer, and therefore aerosol delivery, is also increased by the use of passages through the fuel, which draws hot air to the aerosol generator, especially during suction. The heat transfer is also increased by the preferred heat conducting part, which is spaced from or set back from the ignition end of the fuel element to avoid affecting the ignition and burning of the fuel, and to avoid any invisible penetration, even after use. In addition, the preferred insulating portion tends to confine, direct, and concentrate the heat toward the central core of the article, thereby increasing the heat transferred to the aerosol-forming substance.

Because the aerosol-forming material is physically separated from the fuel element, it is exposed to a significantly lower temperature than that present in the burning cone of fire. This minimizes the possibility of thermal breakdown of the aerosol generator and accompanying aftertaste. This also results

in aerosol production during suction, but minimal aerosol production from the aerosol generating agent during smoldering.

In the preferred embodiments of the invention, the short fuel element, the retracted heat conducting part, the insulating part and/or the passages in the fuel cooperate with the aerosol generator to provide a system that can produce significant amounts of aerosol and possibly tobacco aroma, with practically every puff. The close proximity of the fire cone to the aerosol generator after a few puffs, together with the conductive part,

the insulating part and/or the plurality of passages in the fuel element, results in high heat release both during suction and during the relatively long periods of smoldering between the kites.

Without wishing to be bound by any theory, it is believed that the aerosol generating agent is maintained at a relatively high temperature between the kites, and that the additional heat delivered below the kites, which is significantly increased by the preferred passages in the fuel element, is primarily used to vaporize it aerosol-forming material. This increased heat transfer makes more efficient use of the available fuel energy, reduces the amount of fuel needed and aids in early aerosol delivery.

By suitable choice of fuel element composition, number, size, configuration and arrangement of the fuel element passage, the insulating jacket, the paper wrapping and/or the heat conducting agent, it is also possible to regulate the burning properties of the fuel source to a significant extent. This gives significant control over the heat that is transferred to the aerosol generator, which in turn can be used to change the number of puffs and/or the amount of aerosol delivered to the user.

The combustible fuel elements that can be used in the implementation of the invention are generally smaller than approx. 30 mm long. Preferably, the fuel element is approx. 20 mm or less, more preferably approx. 15 mm or less in length. The diameter of the fuel element is advantageously approx. 8 mm or less, preferably between approx. 3 and 7 mm, and more preferably between approx. 4 and 6 mm. The density of the fuel elements that can be used here varies from approx. 0.5 g/cm<3> to approx. 1.5 g/cm<3> as measured, e.g. by mercury displacement. Preferably, the density is greater than 0.7 g/cm<3>, more preferably greater than 0.8 g/cm<3>. In most cases, a high density material is desirable because it helps 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 desired amount of aerosol.

The fuel elements used here are advantageously cast or extruded from split tobacco, reconstituted tobacco or tobacco substitute material', such as e.g. modified cellulose materials, decomposed or pre-pyrolysed tobacco and the like. Suitable materials include those described in US Patents 4,347,855, 3,931,824, 3,885,574 and 4,008,723 and in Sittig, Tobacco Substitutes, Noyes Data Corp. (1976). Other suitable combustible materials may be used, as long as they burn long enough to simulate the burn time of a conventional cigarette and generate sufficient heat for the aerosol generating agent to produce the desired amounts of aerosol from the aerosol generating material.

Preferred fuel elements include normally combustible carbon materials, such as those obtained by pyrolysis or carbonization of cellulosic materials such as e.g. wood, cotton, rayon, tobacco, coconut, paper and the like. In most cases, combustible carbon is desirable because its high heat-generating capacity and because it produces only minimal amounts of incomplete combustion products. Preferably, the carbon content in the fuel element is approx. 20 - 40 percent by weight or more.

The most preferred fuel elements applicable

in carrying out the invention, carbonaceous fuel elements (i.e. fuel elements that primarily comprise carbon) which are described and claimed in concurrent US applications No. 6S0,604 filed on September 14, 1984, and No. 769,532 filed on August 26, 1985. Carbonaceous fuel elements are especially beneficial 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 particularly preferred embodiments, the aerosol delivered to the user has no significant mutagenic activity when measured by Ames test. See Ames et al., Mut. Res., 31: 347 - 364

(1975); Nagas et al., Mut. Res., 42: 335 (1977).

Fuel additives or combustion modifiers can also be mixed into the fuel to provide suitable burning and glowing properties. If desired, fillers, such as e.g. diatomaceous earth, and binders, such as e.g. sodium carboxymethyl cellulose (SCMC), is also mixed into the fuel. Aromatic substances, such as tobacco extracts, can be mixed into the fuel to add a tobacco flavor or other flavor to the aerosol.

The fuel element is preferably used with one or more passages that extend lengthwise. These passages help regulate heat transfer from the fuel element to the aerosol generating agent, which is important both in transferring heat to produce sufficient aerosol and in avoiding transfer of so much heat that the aerosol generator breaks down. These passages generally provide porosity and increase early heat transfer to the substrate by increasing the amount of hot gases reaching the substrate. They also tend to increase the burn rate.

A large number of passengers, e.g. about. 5 to 9 or more, especially with a relatively large distance between the passages, as in fig. 1A and 3A, produces high convective heat transfer, leading to high aerosol delivery. A large number of passages also usually helps to ensure easy ignition.

High convective heat transfer tends to produce a higher CO content in the mainstream. To reduce C0 levels, fewer passages or a higher density fuel element can be used, but such changes generally tend to make it more difficult to ignite fuel elements and to reduce convective heat transfer, thereby lowering the delivery rate and amount of aerosol. However, it has been discovered that in arrangements where the passages are close to each other, as in fig. IB, so that they burn out or collapse to form one passage, at least at the ignition end, the amount of CO in the combustion products is generally lower than in the same arrangement where the passages are further apart.

The optimal arrangement, configuration and number of fuel element passages must deliver a stable and high aerosol quantity, enable easy ignition and produce small amounts of CO. Various combinations have been investigated in terms of passage arrangement/configuration and/or number of carbonaceous fuel elements used in various embodiments of the invention. In general, it has been discovered that fuel elements with from 5 to 9 passages, which are located relatively close to each other, so that they burn up to one large passage, at least at the ignition end of the fuel element, seem to most closely satisfy the requirements of a preferred fuel element for use in the present invention, particularly for the preferred carbonaceous fuel elements. However, it is assumed that this phenomenon also occurs with the various non-carbon-containing fuel elements that can be used in the execution of the invention.

Variables that affect the rate at which the fuel element passages will collapse during combustion include the density and composition of the fuel element, the size, shape and number of passages, the distance between the passages and their arrangement. For a carbonaceous fuel source with a density of 0.85 g/cm<3> and seven passages of approx. 0.5 mm, the passages should be located within a core diameter, i.e. the diameter of the smallest circle that will circumscribe the outer edge of the passages, between approx. 1.6 and 2.5 mm for them to collapse into one single pass during firing. When the diameter for seven passages is increased to approx. 0.6 mm, however, the core diameter that will collapse during firing will increase to approx. 2.1 to approx. 3.0 mm.

Another preferred arrangement for the passages in the fuel element which is applicable in the embodiment according to the invention is the configuration illustrated in fig. 3B, which has been found to be particularly advantageous for low CO emission and ease of ignition. In this preferred arrangement, a short section at the ignition end of the fuel element is provided with a number of passages, preferably from 5 to 9, which converge into a large cavity 97 extending to the mouth end of the fuel element. The many passages at the ignition end provide the large surface area desired for easy ignition and early aerosol release. The cavity, which can be from approx. 30 to 95%, preferably more than 50%, of the length of the fuel element helps ensure uniform heat transfer to the aerosol generating means and tends to emit little CO to the main stream.

The aerosol-generating agent used in carrying out the invention is physically separated from the fuel element. Physically separated means that the substrate, container or chamber containing the aerosol-forming materials is not mixed with, or part of, the burning fuel element. As noted previously, the arrangement helps reduce or eliminate thermal degradation of the aerosol-forming material and the presence of sidestream smoke. Although not part of the fuel, the aerosol generating agent is preferably in a conductive heat exchange relationship with the fuel element, and preferably abuts or is close to the fuel element. More preferably, the conductive heat exchanger ratio is achieved by means of a heat conductive part, such as e.g. a metal tube or foil, which is preferably withdrawn from or is at a distance from the ignition end of the fuel.

The aerosol-generating agent preferably comprises

one or more heat-stable materials carrying one or more aerosol-forming materials. As used here, a heat-stable material is one that can withstand the high temperatures, e.g. 400 - 600°C, which exists close to the fuel without decomposition or burning. Although not preferred, other aerosol generating agents, such as heat-explosive microcapsules, or solid aerosol-forming substances, within the scope of the present invention, provided they are capable of emitting enough aerosol-forming vapors to satisfactorily resemble tobacco smoke.

Heat-stable materials which can be used as a substrate or a carrier for the aerosol-forming materials are well known to those skilled in the art. Applicable substrates must be porous and must

be capable of retaining an aerosol-forming material,

when not in use and capable of emitting a potentially aerosol-forming . steam when heating fuel elements. Substrates, especially particles, can be placed inside a container, preferably made of a conductive material.

Useful heat-stable materials include heat-stable adsorbent carbons, such as e.g. carbons of porous quality, graphite, activated or non-activated carbons and the like. Other suitable materials include inorganic solids such as ceramics, glass, aluminum oxide, vermiculite, clays such as bentonite and the 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 preferred alumina substrate is SMR-14-1896, available from Davidson Chemical Division of W.R. grace &

Co., which is sintered at elevated temperatures, e.g. higher

than approx. 1000°C, washed and dried before use.

It has been found that suitable particulate substrates can also be formed from carbon, tobacco, or mixtures of carbon and tobacco, into densified particles in a one-step process using a machine manufactured by Fuji Paudal KK, Japan, and sold under the trademark " Marumerizer". This apparatus is described in DE Patent 1,294,351 and US Patent 3,277,520 (now reissued as No. 27,214) as well as Japanese Published Application No. 8684/1967.

The aerosol-generating agent used in the invention advantageously has a distance of no more than approx. 40 mm, preferably no more than 30 mm, most preferably no more than 20 mm from the ignition end of the fuel element. The aerosol generator can vary in length from approx. 2 to approx. 60 mm, preferably from approx. 5 to 40 mm and most preferably from approx. 20 to 35 mm. The diameter of the aerosol generating agent can vary from approx. 2 to approx. 8 mm, preferably from approx. 3 to 6 mm. If a non-particulate substrate is used, it can be equipped with one or more holes, to increase the surface area of the substrate and to increase air flow and heat transfer.

The aerosol-forming material or materials used in the invention must be able to form an aerosol at the temperature present in the aerosol-generating agent when it is heated by the burning fuel element. Such materials will preferably consist of carbon, hydrogen and oxygen, but they may include other materials. The aerosol-forming materials can be in solid, semi-solid or liquid form. The boiling point of the material and/or the mixture of materials can be up to approx. 500°C. Substances with these properties include polyhydric alcohols, such as e.g. glycerol and propylene glycol, as well as aliphatic esters of mono-, di- or polycarboxylic acids, such as e.g. methyl stearate, dodecanedioate, dimethyltetradodecanedioate and others.

The preferred aerosol-forming materials are polyhydric alcohols or mixtures of polyhydric alcohols. Particularly preferred aerosol formers are glycerol, propylene glycol, triethylene glycol or mixtures thereof.

The aerosol-forming material can be dispersed on or

in the aerosol generating agent in a concentration sufficient to penetrate or coat the substrate, carrier or container. The aerosol-forming substance can, for example, be applied at full strength or in a diluted solution by dipping, spraying, vapor deposition or similar techniques. Solid, aerosol-forming components can be mixed with the substrate and distributed evenly in it before formation.

While the charge of the aerosol-forming material will vary from carrier to carrier and from aerosol-forming material to aerosol-forming material, the amount of liquid aerosol-forming materials can generally vary from about 20 to approx. 120 mg, preferably from approx. 35 to approx. 85 mg and most preferably from approx. 45

to approx. 65 mg. As much as possible of the aerosol-forming agent carried on the aerosol-forming agent shall be delivered to the user as WTPM. Preferably, over approx. 2 percent by weight, more preferably over approx. 15 percent by weight and most preferably over approx. 20% by weight of the aerosol generator carried on the aerosol generating means of the user as WTPM.

The aerosol-generating agent can also comprise one or more volatile flavourings, such as e.g. menthol, vanillin, artificial coffee, tobacco extracts, nicotine, caffeine, liqueurs and other substances that impart flavor to the aerosol. It may also include any other desirable volatile, solid or liquid materials. Alternatively, these eventual agents can be launched between the aerosol-generating agent and the mouth end, such as e.g.

in a separate substrate or chamber in the passage leading from

the aerosol-generating agent to the end of the mouth, or in the possible tobacco batch. If desired, these volatile agents can be used instead of part or all of the aerosol-forming material, so that the article emits a non-aerosol flavor or other material to the user.

A particularly preferred aerosol-generating agent comprises the above-mentioned aluminum oxide substrate containing spray-dried tobacco extract, tobacco flavor modifiers, such as e.g. levulinic acid, one or more flavourings, and an aerosol-forming material, such as e.g. glycerol. This substrate can be formed with densified tobacco particles, such as those produced on a Marumerizer, which particles can also be impregnated with an aerosol-forming material.

Articles of the type described here can be used, or can be modified for use, as drug delivery articles, for the delivery of volatile, pharmacologically or physiologically active materials such as e.g. ephedrine, metaproterenol, terbutaline or the like.

As shown in the illustrated embodiments, the smoking article of the present invention comprises a batch or ring of tobacco or a tobacco-containing material which surrounds the aerosol generating agent and which can be used to add a tobacco flavor to the aerosol. In such cases, hot vapors are passed through the tobacco to extract and vaporize the volatile constituents of the tobacco, without combustion or significant pyrolysis. The location of the tobacco charge around the periphery of the aerosol generating means, as shown in fig. 1, 2 and 3, increases the heat transfer to the tobacco, especially in embodiments that employ a thermally conductive member or conductive container between the aerosol-forming material and the peripheral tobacco sheath. The tobacco also acts in these embodiments as an insulating part for the aerosol generator and helps to simulate the feel and aroma of a conventional cigarette.

In addition, another batch of tobacco can be placed inside the aerosol generating means, where the tobacco or densified tobacco particles can be mixed with, or used in place of, the substrate for the aerosol generating materials.

The tobacco-containing material may contain any

any tobacco that is available to the person skilled in the art, such as e.g. "Burley, "Flue Cured", Turkish, reconstituted tobacco, extruded

dry or densified tobacco mixtures, tobacco-containing sheets and the like. Advantageously, a tobacco mixture can be used to add a greater variety to the taste. The tobacco-containing material may also include conventional tobacco additives,

like for example. fillers, casings, reinforcements, such as glass fibres, wetting agents and the like. Flavorings can also be added to the tobacco material, as well as flavor modifying agents.

The heat-conducting part which is preferably used in the implementation of the invention is typically a tube, a strip or a foil of metal (e.g. aluminium) of varying thickness from less than approx. 0.01 mm to approx. 0.2 mm or more. The thickness, shape and/or type of conductive material (eg other metals or "Grafoil" from Union Carbide) can be varied to achieve virtually any desired degree of heat transfer. The heat conducting portion should generally be sufficiently set back to avoid any interference with the ignition of the fuel element, but close enough to the ignition end to provide conductive heat transfer at the early and middle drafts.

As shown in the illustrated embodiments, the heat conducting portion preferably contacts or overlaps the rear portion of the fuel element and at least a portion of the aerosol generating means and is set back or spaced from the ignition end, by at least about 3 mm or more, preferably with approx. 5 mm or more. The heat-conducting part preferably extends over no more than approx. half the length of the fuel element. More preferably, the thermally conductive part overlaps or otherwise contacts no more than approx. the rear 5 mm of the fuel element. Preferred retracted parts of this type do not affect the ignition or burning of the fuel element. Preferred retracted conductive members also help extinguish the fuel as it burns back to the point of contact with the conductor, acting as a heat drain, and does not penetrate, even after the fuel is consumed.

Preferably, the thermally conductive part also forms a conductive container which encloses the aerosol-forming materials. Alternatively, a separate conductive container may be provided, particularly in embodiments using particulate substrates or semi-liquid, aerosol-forming materials. In addition to acting as a container for the aerosol-forming materials, the conductive container improves the heat distribution of the aerosol-forming materials and the preferred peripheral tobacco cabinet and helps prevent aerosol-forming migration to other components of the article. The container also provides a means of regulating the pressure drop through the article, by varying the number, size and/or position of the passages through which the aerosol generator is delivered to the article's nozzle. Also, the container may be provided with peripheral passages or slits to regulate and direct the flow of vapor through the annular tobacco around the aerosol generating means. The use of a container also simplifies the manufacture of the article, by reducing the number of required elements and/or manufacturing steps.

The insulating parts which can be placed around the fuel when carrying out the invention are preferably formed into an elastic jacket of one or more layers of an insulating material.

This sheath is advantageously at least 0.5 mm thick, preferably at least 1 mm thick and more preferably approx. 1.5 to approx. 2 mm thick. The jacket preferably extends over more than half the length of the fuel element. More preferably, it extends over substantially the entire outer periphery of the fuel element. As shown in the embodiment of fig. 2, different materials can be used to isolate the fuel and to surround the aerosol generating agent.

Insulating parts that can be used according to the present invention generally comprise inorganic or organic fibers such as e.g. those made from glass, aluminum oxide, silicon oxide, glass material, mineral wool, carbons, silicones,

boron, organic polymers, cellulosic materials and the like, including mixtures of these materials. Non-fibrous, insulating materials, such as e.g. silica airgel, perlite, glass and the like, formed into mats, strips or other forms, can also be used. Preferred insulating members are elastic to help simulate the feel of a conventional cigarette. Preferred insulating materials must melt during use and must have a softening temperature below approx. 650 - 700°C. Preferred insulating materials should also not burn during use. Slow-burning carbons and similar materials can, however

are used. These materials act primarily as an insulating jacket that retains and directs a significant portion of the heat generated by the burning fuel element to the aerosol generating agent. Because the insulating jacket gets hot near the burning fuel element, to a limited extent, it can also conduct heat towards the aerosol generating agent.

Currently preferred insulating materials for the fuel element include ceramic fibres, such as glass fibers. Two suitable glass fibers are available from Manning Paper Company, Troy, New York, under the designations Manniglas 1000 and Manniglas 1200. Preferred glass fiber materials have a low softening point, e.g. under approx. 650°C, using ASTM test method (C 338-73). Preferred glass fibers include experimental materials manufactured by Owens-Corning, Toledo, Ohio under the designations 6432 and 6437,

which has a softening point of approx. 640°C and melts during use.

Many commercially available inorganic fibers are made with a binder, e.g. PVA, which works so that the structural integrity is maintained during handling. These binders, which would exhibit an unpleasant aroma when heated, must be removed, e.g. by heating in air at approx. 650°C for up to approx. 15 minutes before use. If desired, pectin in an amount of approx. 3% by weight is added to the fibers to provide mechanical strength in the sheath without adding an unpleasant aroma.

Alternatively, the insulating material can be completely or partially replaced with tobacco, either loosely packed or tightly packed. The use of tobacco as a replacement for part or all of the insulating jacket serves an additional function of adding tobacco flavor to the main aerosol stream and producing a tobacco side stream aroma, in addition to acting as an insulator. In these embodiments where the tobacco sheath surrounds the aerosol generating agent and fuel, the sheath acts as a non-burning insulator as well as imparting tobacco flavor to the main aerosol stream.

In embodiments where the tobacco surrounds the fuel, the tobacco is preferably consumed only to the extent that the fuel source is consumed, i.e. up to approx. the point of contact between the fuel element and the aerosol generating agent. This can be achieved by compressing the tobacco around the fuel element and/or by using a conductive heat drain, as in the embodiment in fig. 3. It can also be achieved by treating the cigarette paper wrapper and/or the tobacco with materials that help extinguish the tobacco by

point where it overlaps the aerosol generating agent.

When the insulating portion surrounding the fuel comprises fibrous materials other than tobacco, a barrier may be used between the insulating portion and the mouth end of the article: Such a barrier comprises an annular portion of high-density cellulose acetate rope that abuts the annular material containing tobacco, and which is sealed at both ends with, for example, glue, to block air flow through the rope.

In most embodiments of the invention, the combination of fuel/aerosol generating agent will be attached to a nozzle, which e.g. a foil-coated paper or cellulose acetate/plastic tube as illustrated in the figures, although a nozzle may be provided separately, e.g. in the form of a cigarette holder. This element of the article provides passages that channel the vaporized aerosol-forming materials into the mouth of the user. Due to its length, preferably approx. 35 - 50 mm or more, it also keeps the hot cone of fire away from the user's mouth and fingers and provides sufficient time for the hot aerosol to form and cool before reaching the user.

Suitable nozzles must be inert when applicable

the aerosol-forming substances can have a water- or liquid-proof inner layer, must provide minimal aerosol loss by condensation or filtration and must be able to withstand the temperature in the contact surface with the other elements of the article. Preferred mouthpieces include the cellulose acetate tube used in many of the illustrated embodiments which acts as a resilient outer portion and helps simulate the feel of a conventional cigarette in the mouth portion of the article. Other suitable nozzles will be obvious to the person skilled in the art.

Mouthpieces useful in articles according to the invention may include an optional "filter" tip used to give the article the appearance of a conventional filter cigarette. Such filters include low-efficiency cellulose acetate filters

and hollow or derived (baffled) plastic filters, such as those made from polypropylene. Such filters do not significantly affect the aerosol release.

The full length of the article or any one

part of it may be wrapped in cigarette paper. Preferred paper at the end of the fuel element should openly flame up during burning of the fuel element. In addition, the paper must have adjustable

smoldering properties and should produce a coarse, cigarette-like ash.

In the embodiments that use an insulating jacket

where the paper is burned away from the shrouded fuel element, maximum heat transfer is achieved because the air flow to the fuel source is not restricted. However, paper can be made so that it remains fully or partially intact when exposed to heat from the burning fuel element. Such paper provides limited airflow to the burning fuel element, thereby helping to regulate the temperature at which the fuel element burns and the subsequent heat transfer to the aerosol generating agent.

In order to reduce the burning speed and temperature in the fuel element, and thereby maintain a low CO/C02 ratio, non-porous or zero-porous paper can be used which has been treated so that it becomes slightly porous, e.g. non-combustible mica paper with a number of holes, as an envelope layer. Such a paper regulates the heat release, especially in the middle drafts (ie from drafts 4 to 6).

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

Such paper is known in the cigarette paper field and combinations of such paper can be used to provide different functional effects. Preferred papers used in the articles of the present invention include Ecusta 01788 and 646 plug wrap manufactured by Ecusta, Pisgah Forest, North Carolina, and Kimberly-Clark's KC-63-5, P 878-5, P 878-16-2 and 780 -63-5 paper.

Preferred embodiments of the invention can emit at least 0.6 mg of aerosol, measured as wet total particulate matter (WTPM), in the first three puffs when the article is smoked under FTC smoking conditions. (FTC smoking conditions consist of two second puffs (35 ml total volume) separated by a 58 second smolder.) More preferred embodiments of the invention may deliver 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 three puffs when the article is smoked under FTC smoking conditions. Preferred embodiments according to the invention also emit an average of at least approx. 0.8 mg wet, total, particulate matter per drag for at least approx. 6 puffs, preferably for at least approx. 10 puffs, under FTC smoking conditions.

Claims (5)

1. A cigarette-type smoking article, comprising a carbonaceous fuel element (10, 24) at the ignition end of the smoking article, which element optionally includes one or more longitudinal passages (16) extending therethrough; a physically separate aerosol-generating means (12) which includes an aerosol-forming material, the aerosol-generating means (12) being located between the fuel element (10, 24) and the mouth end (15) of the article, and additionally possibly including a heat-conducting element (26 , 50, 52, 70, 74, 90) arranged to conduct heat from the fuel element to the aerosol-generating means, characterized in that a ring of tobacco-containing material (72, 88) circumscribes at least part of the aerosol-generating means (12). 2. Smoking article according to claim 1, characterized in that the ring of tobacco-containing material (72, 88) additionally includes an insulating material. 3. Smoking article according to claim 2, characterized in that the insulating material is insulating fibres. 4. Smoking article according to any one of the preceding claims, characterized in that the ring of tobacco-containing material (72, 88) additionally surrounds at least part of the fuel element (10, 24). 5. Smoking article according to claim 1, characterized in that at least part of the ring of tobacco-containing material (72, 88) includes a mixture of tobacco and glass fibers.