US 3356094 A
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Description (OCR text may contain errors)
Dec. 5, 1967 c. D. ELLIS ET AL 3,356,094
' SMOKING DEVICES F'iled Sept. 22, 1965 ATTORN EYS United States Patent ABSTRAQT OF THE DISCLOSURE A smoking device of the type resembling a cigarette including an external wrapper and a tubular element having an internal air passage or space and concentrically arranged with respect thereto and having an annular space between the wrapper and the tube with tobacco being disposed in one of the spaces. The tube being of a material which is destructible by heat from the burning tobacco or otherwise frangible or friable so that while burning the tobacco the tube can be readily knocked away with the accompanying ash, the device being arranged to provide for the passage of air through the tube and through the tobacco section to the mouthpiece end of the device and having means for controlling the relative proportion of air drawn through the tobacco section whereby a satisfying smoke is obtained by the user when the device is smoked.
This invention pertains to improvements relating to smoking devices, particularly smoking devices of the type having the appearance of a traditional smoking device, such as a cigarette, but which contain a composition which releases nicotine vapor and aerosol forming materials when subjected to an elevated temperature below the ignition point of the composition. Smoking devices of this type are shown in copending US. patent application, Ser. No. 342,869, filed Feb. 4, 1964, by Charles Drummond Ellis, Herbert Schachner and David Williamson now United States Patent No. 3,258,015, granted June 28, 1966.
Smoking devices of this type, as disclosed'in the aboveidentified application, generally comprise two coaxial but separate regions, one of which contains a source of nicotine and aerosol and the other of which contains a heating material such as tobacco which serves to heat the source material in the first region and cause the release of the nicotine and aerosol. These two regions may be formed by an outer cylindrical wrapper such as a cigarette wrapper and a coaxial centrally located tube. The tube may contain the source material for the nicotine and aerosol and may communicate with a mouthpiece through which the smoker can draw in air and also the combined aerosol and nicotine into his mouth-The annular space between the tube and'wrapper may contain the heating material and, in the above referred to patent application, the heating material was completely isolated from the mouthpiece. Furthermore, the central coaxial tube in the smoking devices of the above patent application was not heat consumable with the result that, as the tobacco or other heating material in the annular region-was consumed, the tube would remain protruding beyond the end of the smoldering cone of the smoking device.
The tube protruding from the partially smoked smoking device and also the complete absence of any products of combustion or smoldering from the aerosol drawn into the mouth of the smoker served to detract somewhat from the realistic appearance of the smoking device.
It is an object of the present invention to overcome the above-indicated problems and to provide an improved smoking device which more closely simulates a true cigarette in appearance and in smoking characteristics while still avoiding the major proportion of the unnecessary and undesired contents of the smoke stream.
According to the present invention the central tube is made of a frangible or friable material or comprises material which becomes frangible or friable under the influence of heat. The tube can then be readily knocked away with the accompanying ash as the device is smoked and does not project in unsightly fashion. The conventional appearance of a cigarette can thus be better maintained. Such a tube may be composed of a plurality of tube segments held together axially by an adhesive which will lose its strength under the influence of the heat or by a sleeve or envelope which will become frangible under the influence of the heat. Alternatively, the tube may be made of a material comprising an inorganic salt which loses water and/or carbon dioxide and becomes brittle under the influence of the heat.
Also, in accordance with the present invention, the tobacco or heating material is not isolated from the mouthpiece and air is drawn into the mouth of the smoker through both regions, i.e., through the nicotine source material inside the tube and the burning or smoldering tobacco outside the tube. Thus, the smoker draws into his mouth not only the nicotine containing aerosol but also a certain amount of ordinary smoke from the combustion of the tobacco. Due to the presence of the nicotine containing aerosol, only a small proportion of smoke, for example 10%, may be sufiicient to give the required effect. A total and satisfying smoke can be obtained with a high nicotine to tar ratio or, as sometimes expressed, a low ratio of total particulate matter (T.P.M.) to nicotine. This latter ratio can readily be reduced to one-quarter or less of the values normally expected of smoke from cigarettes having no special provision for reducing the ratio. If desired, the nicotine content may be made normal, but with little of the normal particulate and vapor phases.
The desired results can be achieved by arranging both regions of the smoking device, i.e., the regions inside and outside the tube, so as to communicate directly with the mouthpiece and controlling the relative draw resistance from the two regions so as to control the mixture entering the smokers mouth. Alternatively, the outer region surrounding the tube and containing the tobacco or other heating material may be isolated from direct communication with the mouthpiece and the central tube may be perforated at intervals to allow the smoke to pass from the annular space surrounding the tube into the said tube. In this case the relative mixture can be controlled by the size and spacing of the perforations.
Thus, when the smoking device is smoked the smoker will draw into his mouth a small amount of smoke adequate to satisfy the taste of the smoker along with the nicotine containing aerosol. In addition, the combustion in the annular space will be, at least to some extent, under the smokers control. When he puffs he will detect the familiar brightening of the smoldering cone of the tobacco and the resemblance to a conventional cigarette will be heightened. Furthermore, the admission of smoke from the annular space may assist in the even formation of the aerosol. Finally, it should be pointed out that no unsightly tube will project from the partially smoked smoking device, with the result that the similarity to a cigarette will be heightened.
Although the invention thus seeks primarily to furnish a smoking device which will yield nicotine in an acceptable form, both psychologically and physiologically, but without the necessity for taking into the system so much of the products of combustion as is usual when smoking a conventional cigarette, it may also be used mainly or partially as a means for achieving greater freedom for influencing the taste of the smoke, for introducing flavors and so forth.
This also may be one of the principal purposes where the invention is applied to a cigarette which is of a conventional nature except for the provision of a central tube, both the central tube and the annular space having communication with the mouthpiece. The tube may contain an essence or other flavor from which it is desired to impart a flavor to the smoke without subjecting the material to the high temperatures of combustion of the burning tip. The release of flavoring material can be controlled by appropriate control of the temperature and location of the material inside the tube and materials which would be destroyed if incorporated into normal cigarettes can be employed.
In the accompanying drawings:
FIG. 1 is a longitudinal sectional view through one form of smoking device embodying our invention;
FIGS. 2 to 4 are similar sectional views through three other forms of such smoking devices; and
FIG. 5 is a detailed sectional view on an enlarged scale showing a modified form of central tube construction that may be used in any of the smoking devices shown in FIGS. 1 to 4.
In the accompanying drawings we have shown several forms of our smoking device. Each of the devices has an elongated cylindrical body element having the general size and configuration of a cigarette so that it can be readily carried and manipulated in the hand of a user. Each form of the device has a mouthpiece end 12 which is inserted in the mouth of the smoker and an outer or ignition end 14. The smoking device is encased in a wrapper 11 which is preferably porous cigarette paper but may also be made of reconstituted tobacco or similar material. The mouthpiece end is preferably provided with a tip 13 which, as shown, extends circumferentially around the wrapper at the mouthpiece end. It also extends in disc-like fashion across the mouthpiece end of the cigarette and has a central aperture through which the air stream and entrained products may be drawn. The tip may be made of heavy gauge paper or cork or other similar material.
As indicated above, the smoking device should preferably simulate a cigarette in appearance. Thus, it may be between 70 mm. and 85 mm. in length and between 7 mm. and 20 mm. in diameter. It should be understood, however, that these dimensions are merely suggested so that the smoking device will simulate the appearance of a conventional cigarette and that the length and diameter may both be varied beyond the indicated limits. Extending longitudinally of the smoking device and centrally thereof in concentric relationship with the wrapper 11 is the tube shown at 16 in FIGS. 1 and 2, at 16' in FIGS. 3 and 4 and at 16" in FIG. 5. The tube extends from the outer or ignition end 14 to a point adjacent the end of the tip 13 at the mouth end where it communicates with the aerosol nucleating or condensing chamber 15. The tube is open at both ends so that the air stream and entrained material can be drawn therethrough.
The tube divides the interior of the smoking device into two spaces or regions, i.e., the space inside the tube and the annular space between the tube and the wrapper. In one of these spaces is disposed a source of additive material which may be nicotine or a flavoring material which is released when subjected to an elevated temperature below a temperature where major decomposition of the nicotine or flavoring material occurs. In the other space heating material, such as finely cut tobacco, is provided which, when ignited, serves to heat the source material.
In the illustrated embodiment the source of additive material is coated on the inside of the tube, as shown at 17, and the heating material or finely cut tobacco is disposed in the annular space, as shown at 18.
The source of additive material 17 is preferably a nicotine source material, for example acompositioncon- 7 sisting of approximately of nicotine extract or tobacco concentrate and approximately 15% of colloidal silica. The nicotine extract or tobacco concentrate may be prepared in the manner indicated in the aforesaid patent application, Ser. No. 342,869, as for instance 'by macerating tobacco with petroleum ether to remove waxes and some of the resins. The mixture is then filtered and the filtrate discarded. The extracted tobacco is then reextracted with chloroform yielding a fraction of approximately 5 to 10% of the weight of the tobacco which is rich in nicotine and flavoring acids. This material may then be evaporated to further concentration or dryness. A concentrated solution of the material or a water slurry of the residue mixed with colloidal silica in the above indicated proportions is then coated on the inner surface of the tubular member 16.
The heating material 18 preferably comprises finely cut tobacco, reconstituted tobacco or mixtures thereof cut to between approximately and 200 cuts per inch. A small quantity of a smoldering enhancing compound in the order of approximately 5% by weight, such as sodium or potassium chlorate or sodium or potassium nitrate, may be mixed with the finely cut tobacco. The tobacco in the annular space is preferably packed to a density of approximately 0.25 to 0.35 g./ cc. The tubes 16, 16' and 16" are made of a frangible or friable material or are made of a material which becomes frangible or friable under the influence of the heat from the burning tobacco 18.
When cold, the tube should have adequate strength to resist shocks encountered in manufacturing and handling. In the course of the smoking of the device, however, as the zone of combustion or cone of the smoldering tobacco travels from the ignition end towards the mouthpiece end, the material of the tube is destructively affected or it is rendered frangible or friable so that the end portion of the tube projecting beyond the smoldering zone can be readily discarded with the ashes by tapping or agitating the smoking device.
This result can be achieved in any desired manner. In FIGS. 1 to 4 the tubes 16 and 16' may be made from inorganic salts which lose water of hydration and/or carbon dioxide when heated. Mixed with water and a plasticizer the salt may be extruded to the desired tubular shape which is retained after drying it at room temperature. A preferred combination is magnesium sulfate heptahydrate as the salt and colloidal silica as the plasticizer. Alternate salts are, for example, magnesium carbonate trihydrate, basic carbonates of magnesium, sodium or potassium bicarbonate and calcium sulfate. Alternate plasticizers are magnesium oxide, ground chalk or kaolin. Suitable ranges of proportion are from 27 to 85% by weight of the salt and 8 to 45% of the plasticizer and 7 to 28% of water. Preferred proportions are approximately 70% of the salt, 9% of the plasticizer and 21% of water. The external and internal diameters of the tube may be varied depending upon the diameter of the smoking device. We have found that satisfactory results are obtained where the external diameter is between 1 and 3 mm., prefer-ably 2.5 mm., and the internal diameter is between 0.5 and 2 mm., preferably 1.5 mm.
Byway of specific example, a mixture of the aforesaid preferred percentages of magnesium sulfate heptahydrate, colloidal silica and water can be extruded under a pressure of 300 kg./cm. to form a tube with an external diameter of 2 mm. and an internal diameter of 1.2 mm. which is dried at room temperature for 24 hours to produce a finished rigid tube. The tubes are provided in lengths of approximately 70 mm. and are coated internally with the source of nicotine extra-ct and colloid-a1 silica as described above. The tubes are then incorporated in smoking devices of the type described above. When a device incorporating one of the tubes is smoked, the tube disintegrates adjacent the smoldering cone and falls away as the tobacco ash is discarded.
An alternate form of fnangible tube may be made from a ceramic material having silicate particles bonded therein by means of a small proportion of an epoxy resin having a softening point of approximately 25 C. The material for the tube may be prepared by sintering the ceramic component in the presence of the resin.
Instead of lining the inside of the tube with the sOurce of nicotine and aerosol forming material, as shown at 17, the nicotine source material may also be absorbed or otherwise incorporated in the material of the tube. Under those circumstances the nicotine or tobacco extract is mixed directly with the inorganic material.
A specific example of such a mixture is as follows:
Parts by weight Magnesium sulfate heptahydrate 64.5 Colloidal silica 8 Nicotine 4.9 Water 22.6
An alternate example is as follows:
Parts by weight Magnesium sulfate heptahydrate 56 Colloidal silica 10 Water 16 In both of the foregoing examples, the inorganic material is finely milled, using a ball mill for approximately 24 hours. The mixture is extruded in the manner described above to produce the tubing. The extruded tubing is extracted and dried at 20 C. for 24 hours and it is then ready for use.
In FIG. 5 we have shown an alternate form of tube 16" composed of a'series of short segments made of a suitable material such as a ceramic material which are connected together in axial relationship by a suitable adhesive, as shown at 26. The adhesive should be of the type that has moderate strength at room temperature so as to retain the tube in assembled relationship. Onheating to an elevated temperature, namely a temperature between 100 and 500 C., the adhesive should melt, soften or decompose sothat the segment projecting beyond the smoldering cone can be readily discarded when the cigarette is tapped to discard the ashes. The adhesive selected and the products of decomposition thereof should not have an adverse effect upon the quality or flavor of the smoke nor should it be injurious to health. For this purpose we prefer to use polyethylene but other thermoplastic material, such as polypropylene, nylon and polystyrene may also be employed. Natural gums, starch paste, methyl, ethyl or carboxy methyl cellulose or cellulose acetate may also be employed.
A tube 16" made of separate segments, as shown in FIG. 5, may alternatively be held together by a tubular envelope or sheath of heat destructible material, such as cigarette paper. A suitable paper should have a porosity between therange of 80 to 250 ml. per minute and should give a non-clinging or semi-clinging ash. When the device is smoked, the envelope will burn with the tobacco and the segments will be left progressively free to fall away.
It will be seen that in the several forms of device shown in the drawing and described above, the tube 16, 16' or 16" will progressively break away or fall away as the smoking device or cigarette is smoked.
Tubes of the type illustrated in FIGS. 1 to 5 and described above may be used in smoking devices such as shown in the aforesaid copending application, Ser. No. 342,869, filed Feb. 4, 1964, or alternatively they may be used in conventional cigarettes so as to impart nicotine, flavoring material and other additives to the smoke stream or so as to introduce additional air into the smoke stream.
As illustrated herein, tubes of this type may also be incorporated in modified and improved smoking devices of the type disclosed in the aforesaid patent application, Ser. No. 342,869, but in which a small amount of smoke or the products of combustion are mixed with the air stream containing the aerosol and nicotine. In the several devices shown in FIGS. 1 to 4, inclusive, a small quantity of smoke and the products of combustion from the burning tobacco 18 is drawn into the mouth along with the air stream containing the aerosol and nicotine with the mixture of smoke and aerosol material being in controlled proportions. Thus, as shown in FIG. 1, the annular space containing the tobacco material 18 communicates directly with the aerosol nucleating chamber 15. When the tobacco is ignited at the outer end thereof and the smoker draws air through the aperture in the tube of the cigarette, the heat from the burning tobacco releases nicotine and aerosol forming materials from the coating 17 and these materials are drawn with the air stream into the aerosol nucleating chamber 15 where the aerosol particles are formed and the nicotine is deposited thereon. Simultaneously, smoke from the burning tobacco is drawn into the chamber 15 and the particles therein serve to nucleate the formation of the aerosol particles and the condensing of the nicotine thereon. Due to the fact that the tube 16 is open at its outer end, there is substantially less pressure drop through the tube than through the tobacco material 18, with the result that the major proportion of the stream drawn through the tip of the cigarette into the mouth would go through the tube 16. In order to control the relative proportion of materials, a restriction 20 may be formed at the mouthpiece end of tube 16 and this restriction may be formed integrally with the tube or it may be separately formed as from ceramic material and adhered to the inner end of the tube, or it may be a separate insert provided in the end of the tube. The restriction 20 may by cylindrical or of any other suitable configuration.
The restriction 20 increases the pressure drop of the path through tube 16 so that the smaller its size, the larger will be the proportion of each puff volume drawn through the annular space containing the tobacco 18.
We have found that satisfactory results are obtained where the pressure drop through the tube and restriction is within the range of 1 to 20 cm. (water gauge) at 17.5 cm. /sec. and preferably between 6 and 16 cm. For the aforesaid range, the restriction may be between 2 and 10 mm. and preferably between 4 and 6 mm. in length and between 0.4 and 1.2mm. and preferably 0.7 to 0.9 mm. in width.
To illustrate the elfect of the restriction 20, such as shown in FIG. 1, smoking devices were prepared (a) without a restriction and (b) and (c) with restrictions of the same length, 5 mm., but different internal diameters. The general dimensions of the smoking device are as follows:
Mm. Length Internal diameter 10 External diameter of tube 16 2.5 Internal diameter of tube 16 1.5
Without With With Insert Insert Insert Internal diameter (mm) 1. 5 0.85 0.75 Pressure drop (cm. water guage) of tube 16 at 17.5 crnfi/sec 1 8 12 Weight of nicotine in tube 16 (mg) 4. 7 4. 3 4. 5 Yield of nicotine in smoke (mg). 1. 5 1. 6 1. 5 Yield of T.P.M. in smoke (mg) 6. 6 13.1 16. 7 Ratio T.P.M./nicotine 4. 4 8.2 11.1
The smoke from (b) and (c) was less irritating and had characteristics approaching those of normal cigarette smoke. As will be seen, a wide control of the total particulate matter to nicotine ratio is possible.
In addition to the restriction 20 or, at times, instead of using the restriction 20, a filter may be provided between the annular space containing the tobacco 18 and the chamber 15 for controlling the proportion of smoke drawn in from that space. Such a filter is shown at 22 in FIGS. 2 and 4. The filter may be made from any of the materials normally used for cigarette filters, for example, cellulose acetate, paper, viscose, bonded carbon, or the like. The pressure drop for the filter may be within a range of 0.1 to 2.0 cm. water gauge at a flow rate of 17.5 cm. /sec. and is preferably between 0.2 and 1.0 cm. It may have a length within the range of'2 to 20 mm. and is preferably between 2 and 5 mm.
Such a filter affords an additional means for controlling the aforesaid significant ratio. Increased pressure drop in the filter will reduce the ratio.
Using devices having the above-described general dimensions the following results were obtained: ((1) without a filter and (e) and (f) with annular cellulose acetate filters such as shown at 22 of different lengths arranged as in FIG. 2.
l (a) (e) i Length of filter 22 (rnrrr) h 2 10 Pressure drop (cm. W.G.) of filter 0.2 1.1 Weight of nicotine in tube 16 (mg.) 4. 7. 7 7. 6 Number of pufis 12 10 11 Yield of nicotine in smoke (mg) 1. 5 1. 8 1. 2 Yield of T.P.M. in smoke (mg) 16. 7 15.0 6. 7 Ratio T.P.M.lnicotine 11.1 8.3 5.6
A wide control of the ratio is again available.
In the smoking device illustrated in FIG. 3, the tube 16' is perforated with holes 24 distributed uniformly along its length and around its circumference. The annular space containing the tobacco 18 is closed at the mouthpiece end by an annulus 25. Both the tube 16 and the annular space are open at the outer end 14. When the device is smoked, smoke from the smoldering tobacco is drawn into the tube 16 through perforations 24 where it mixes with the air drawn through the tube and containing the nicotine and aerosol material.
Holes 24 of various shapes other than the round shape shown may be employed and they may vary in number between 2 and 50 per cm. of length of tube 16. The area of each hole may be between 0.002 and 0.12 cm.
The following results (g) were obtained with a smoking device of the above stated general dimensions and with a tube 16 having a length of 70 mm. and with 12 holes per cm. length, each with an area of 0.005 cm. arranged as in FIG. 3.
(a) Weight of nicotine in tube 16 (mg) 3.2 Number of puffs 11 Yield of nicotine in smoke (mg) 1.7 Yield of T.P.M. (mg) 7.5 Ratio T.P.M./ nicotine 4.4
If desired the annular space containing the tobacco 18 of the device of FIG. 3 may be in open or restricted communication with the mounthpiece, for example, through apertures in the annulus 25.
Instead of being provided with apertures 24, the tube 16 may be made of a smoke previous or porous material, as for example, a sintered material.
It is also possible to provide a smoking device having a combination of the features described above for controlling the proportions of the products of combustion and the air stream containing the nicotine and aerosol material, as shown in FIG. 4. Thus, the smoking device of FIG. 4 has a restriction 20, an annular filter 22 between the tobacco and the chamber and a perforated tube 16. Alternatively, the restriction and perforated tube 16' may be used together but without the filter 22.
Results obtained from such a combination (h) without a filter and (i) with the filter 22 are as follows:
Length of filter 22 (mm) 5 Pressure drop (em. W.G.) of filten. 0.5 Number of holes 24/cm 12 Area of each hole (sq. em.) 0.005 0.005 Pressure drop (cm. W.G.) of restriction 20 at 17.5
cmfi/sec 12 12 Length of restriction (mm.) 5 5 Diameter of restriction (1pm.) 0.75 0.75 Weight of nicotine in tube 16 (mg). 9. 8 10.2 Number of puffs. 17 18 Yield of nicotine in smoke (ing) 1. 7 2. 2 Yield of I.P.M. in smoke (mg)... 11.0 9.2 Ratio T.P.M./nicotine G. 5 4. 2
Smoking devices to which the present invention 18 applied may, in other respects, be similar to the device described and illustrated in the aforesaid patent appllcation,
Ser. No. 342,869. For example, the tube 16 or 16 may be made of non-frangible or non-friable material which is unaffected by the heat from the tobacco. In addition the tube may be made of slowly combustible materials, for example, an extruded tobacco composition, so that it will slowly burn away as the device is smoked.
In addition, central tubes and restrictions, filters and/ or perforations such as above described and illustrated herein, may be applied to what are otherwise normal cigarettes and the layer 17 may then consist of a flavoring additive or essence, for example, methol, vanillin, or the like.
It will thus be seen that we have provided an improved smoking device having a controlled ratio of nicotine to total particulate material and which closely resembles a conventional cigarette in appearance, psychological factors and smoking characteristics.
Modifications may be made in the illustrated and described embodiment of our invention without departing from the invention as set forth in the accompanying claims.
1. An improved smoking device assembly having a mouthpiece end and an ignition end through which air may be drawn comprising: a cylindrical wrapper formed around the device and extending longitudinally thereof; a central tube arranged concentrically therein so as to provide a space inside the tube and an annular space between the wrapper and tube, said tube being made of a material selected from the group consisting of materials which are destructively affected by heat from the burning tobacco, frangible materials and materials which are rendered frangible at the burning temperature of the tobacco material so that any portion of the tube projecting beyond the burning end of the tobacco material can be readily eliminated; a source of additive material releasable into the air when subjected to an elevated temperature disposed in one of said spaces; tobacco material disposed in the other of said spaces so as to heat said source of additive material when it is ignited and means controlling the relative proportion of air passing through the respective spaces.
2. A improved smoking device as set forth in claim 1 in which the source of additive material is a source of nicotine.
3. An improved smoking device as set forth in claim 1 in which the source of additive material is contained in the space within the tube and the tobacco material is contained in the annular space between the wrapper and tube.
4. An improved smoking device as set forth in claim 3 in which means are provided for blocking direct communication between the annular space and the mouthpiece end and the tube is perforated so that the annular space communicates with the mouthpiece end through the space inside the tube.
5. An improved smoking device assembly having a mouthpiece end and ignition end through which air may be drawn comprising: a cylindrical wrapper formed around the device and extending longitudinally thereof; a central tube arranged concentrically therein so as to provide a space inside the tube and an annular space between the wrapper and tube; said tube being made of a material selected from the group consisting of materials that are destructively affected by heat from the burning tobacco, frangible materials and materials which are rendered frangible at the burning temperature of the tobacco material so that any portion of the tube projecting beyond the burning end of the tobacco material can be readily eliminated; a source of additive material which releases nicotine vapor and aerosol forming materials including water vapor into the air drawn through the tube when subjected to an elevated temperature disposed in the space inside said tube and arranged so as to provide a continuous unobstructed air passage from one end of the tube to the other; tobacco material disposed in the annular space so as to heat said source of additive material when it is ignited; said assembly being arranged to provide for air passage from the ignition end through the spaces to the mouthpiece end and including an aerosol nucleating chamber between the source of additive material and the mouthpiece end and being arranged so that the aerosol forming materials cool and condense into aerosol particles and so that nicotine vapor contacts said aerosol particles and condenses thereon.
6. An improved smoking device as set forth in claim in which a restriction is provided adjacent the mouthpiece end of the tube so as to restrict the amount of air drawn through the tube to the mouthpiece end.
7. An improved smoking device as set forth in claim 5 in which an annular filter is provided between the annular space and the mouthpiece end of the tube.
8. An improved smoking device as set forth in claim 5 which includes means controlling the relative proportion of air passing through the respective spaces.
9. An improved smoking device as set forth in claim 1 wherein the tube is composed of a plurality of tube segments held together coaxially by an adhesive which loses its strength under the influence of heat.
10. An improved smoking device as set forth in claim 1 wherein the tube is made of a material comprising an inorganic salt which loses water or carbon dioxide and becomes brittle under the influence of heat.
11. An improved smoking device as set forth in claim 10 wherein the material from which the tube is made is magnesium sulfate heptahydrate.
12. An improved smoking device as set forth in claim 11 wherein the material from which the tube is made contains colloidal silica.
13. An improved smoking device as set forth in claim 1 wherein the tobacco material is disposed in the annular space and the source of additive material is disposed in the space inside the tube and releases nicotine vapor and an aerosol forming material including water vapor when heated and an enlarged aerosol nucleating chamber is disposed between said source material and the mouthpiece end of the smoking device.
14. An improved smoking device assembly having a mouthpiece end and an ignition end through which air may be drawn comprising: a cylindrical Wrapper formed around the device and extending longitudinally thereof; a central tube having perforations therein and arranged concentrically therein so as to provide a space inside the tube and an annular space between the wrapper and tube; a source of additive material which is releasable into the air when subjected to an elevated temperature contained in the space within the tube; tobacco material contained in the annular space between the wrapper and the tube; said assembly being arranged to provide for air passage from the ignition end through the spaces to the mouthpiece end; and means adjacent the mouthpiece end of the device blocking direct communication between the annular space and the mouthpiece end so that the annular space communicates with the mouthpiece end only through the perforations in the tube.
References Cited UNITED STATES PATENTS 977,635 12/1910 Klein 131-9 2,349,551 5/1944 Helm 131-10 X 3,162,199 12/1964 Moll 131-9 3,258,015 7/1966 Ellis et al 131171 FOREIGN PATENTS 752,358 7/1956 Great Britain.
LUCIE H. LAUDENSLAGER, Primary Examiner.