US3349776A

US3349776A - Low-temperature cigarette

Info

Publication number: US3349776A
Application number: US416022A
Authority: US
Inventors: James A E Bell; David H Laing
Original assignee: Bell Canada Inc
Current assignee: Bell Canada Inc
Priority date: 1964-12-04
Filing date: 1964-12-04
Publication date: 1967-10-31
Anticipated expiration: 1984-10-31

Description

J. A. E BELL ETAL.

LOW- TEMPERATURE CIGARETTE Filed Dec.

I N V EN '1 ORE M M51; A. @ELL MWD m. was;

NW haw 9W MTEMT AQENT f United States Patent 3,349,776 LOW-TEMPERATURE CIGARETTE James A. E. Bell, Cooksville, Ontario, and David H.

Laing, Hornby, Ontario, Canada, assignors of onethird each to said Bell, said Laing and James Dennis Jones, Willowdale, Ontario, Canada as tenants in common Filed Dec. 4, 1964, Ser. No. 416,022 17 Claims. (Cl. 1318) ABSTRACT OF THE DISCLOSURE The invention is a cigarette having in an outer extent, tobacco of a higher defined density surrounding a longi tudinally extending column of a lower defined density and of limited cross-section relative to the cross-section of the cigarette. Preferably on the cigarette there is an extent or filter of defined density inward of the outer extent.

This invention relates to a cigarette.

By cigarette we mean a small quantity of cut tobacco, extending longitudinally, bounded on its sides by paper or other combustible casing; and, in cross-section, usually of cylindrical shape, although the shape may be oval or elliptical.

It has been shown by recent investigation into mortality effects of smoking, such as that of the US. Surgeon-Generals Advisory Committee on Smoking and Health, that the average mortality ratio for smokers of cigarettes is 1.70 to 1.

By mortality ratio in relation to smokers is meant: the number of deaths per thousand smokers in a given interval, divided by the number of deaths per thousand non-smokers in the same interval, other factors being equal, as far as is known.

Compared to the 1.70 to 1 average mortality ratio for cigarettes found by the Surgeon-Generals Committee, the corresponding average ratio for cigars is 1.05 to 1 and that for pipes is 1.01 to 1.

From this it will be seen that whereas cigarette smoking seriously increases the risk of death, the risk of death to a cigar or pipe smoker is barely different from the mortality prospects of a non-smoker.

It is an object of this invention to provide a cigarette which will be as safe for the user as a cigar or pipe, but which in other respects, including drawing quality and flavour, will resemble a normal cigarette.

It is an object of the invention to provide a cigarette having a much lower average maximum temperature of combustion (attained when the user is drawing on it) and also a lower temperature when air is not being drawn through the cigarette, such time being known hereafter as .idling.

During the combustion of hydrocarbons of the type found in tobacco, two types of reaction take place, namely: pyrolytic reactions and oxidation-reduction reactions. The former reaction includes distillation, dehydrogenation, cracking, rearrangement, and condensation, while the later reaction includes reaction of the hydrocarbons with 3,349,776 Patented Oct. 31, 1967 The extent and products of the oxidation reduction reactions will depend mainly, and possibly solely, on the combustion temperature, the degree of oxidation and the rate of gas-flow through the combustion zone.

It is found that the quantity and the type of the product of the pyrolytic and oxidation-reduction reactions are affected substantially solely by the temperature, the time at temperature, and the rate of gas-flow through the combustion zone, and it will be noted that an increased gasflow rate will have an enhanced effect upon the oxidation reactions since the latter are exothermic.

It is an object of this invention to provide a cigarette wherein the average maximum temperature during smoking is much lower than in conventional cigarettes and of the same order as the average maximum temperature of a pipe or cigar.

In Table I following are the tables for the idling temperature, the maximum temperature and the degree of oxidation in a pipe, cigarette and cigar.

Temperatures in the tobacco during smoking were meas ured on a high-speed recorder using 0.006" (34 gauge) chromel-alumel thermocouples completely embedded in the tobacco. Standard 35 ml. puffs of two-second duration were used at various puff rates in order to simulate actual smoking conditons.

The degree of oxidation was measured by measuring the CO /CO ratio of the smoke employing conventional Orsat gas analysing equipment. Standard puffing techniques were again employed.

The results of the investigation did not vary excessively from one to six puffs per minute. The results are reported in Table I below as average values, indeed the average values are more useful as they eliminate the personal factor of different putting rates. The mortality ratios as reported by theSurgeomGenerals Advisory Committee on Smoking and Health are also included in Table I for comparative purposes.

The term average maximum temperature is the temperature in the hottest part of the combustion zone during a puff cycle. With the inventive cigarette hereinafter defined, having volumes filled with tightly packed tobacco, the term average maximum temperature is the temperature in the hottest part of the combustion zone. in such tightly packed tobacco. The idle temperature is the temperature of the combustion zone with no induced gas flow therethrough.

It will be noted that the average maximum temperatures of pipe and cigar are considerably lower than the same temperatures for the cigarette, and that the idling temperature is similarly lower.

It is an object of the invention to design a cigarette which will simulate the combustion temperatures of a cigar or pipe at maximum and at idle temperature.

It is an object of this invention to provide a cigarette wherein the tobacco to be smoked is more tightly packed than in previous cigarettes, whereby the forced flow of air and combustion products during smoking and the natural flow of air through the cigarette during idling, is lower than with conventional cigarettes, and hence the smoking and idling temperatures are lower.

It is an object of this invention to provide a cigarette wherein the majority of the tobacco is more tightly packed than heretofore, reducing by the decrease in passages and the decrease in passage size between tobacco particles, the ease of air flow therethrough, but wherein columns without tobacco, or of tobacco of lesser density, are provided, extending the length of the smokable portion of the cigarette, and surrounded by such tightly packed tobacco, whereby the air may flow at the same average rate across the cigarette as a whole, while flowing at a lesser rate through the tightly packed tobacco, including the combustion zone thereby creating a lower average maximum temperature.

It is an object of this invention to provide a cigarette wherein the tobacco is more tightly packed than heretofore, reducing by the decrease in passages between tobacco particles and the decrease in passage size, the ability of convective flow of air and the gases of combustion to take place, thereby creating a lower idle temperature.

It is an object of this invention to provide a cigarette having an idle temperature of about 530 C. and an average maximum temperature of about 665 C., in the manner measured, the respective values, as will be seen from Table I, being somewhere between the characteristics of a cigar and a pipe and much lower than those of a conventional cigarette.

By average maximum temperature with the invention, we mean the average temperature of the hottest part of the combustion zone in the densely packed tobacco in the inventive cigarette during a number of puffs. The invention provides a cigarette, wherein at least the majority of the tobacco forming the portion to be smoked and located toward the farther end from the smokers mouth (referred to herein as the outer extent) is more tightly packed than previously, whereby, during the idling period, the natural convection flow caused by combustion cannot move through the tobacco at any rate comparable with the rate in the conventional cigarette. There is provided a column or columns of lessened density of tobacco or free of tobacco extending down the smokable portion of the cigarette and surrounded by such tightly packed tobacco, whereby a low resistance flow path is provided for smoke drawn down the cigarette from the fireball to the smoker. A filter or other flow impedance (which may be tobacco itself) is attached, designed to provide an inner extent nearer the smokers mouth (hereinafter referred to as the inner extent) wherein the fiow impedance is designed to balance the combined effects on overall flow characteristics, of the tightly packed tobacco on the one hand and the column of reduced density on the other, and to provide a cigarette having overall the same drawing qualities as a conventional cigarette. As a result of this design, some of the air travelling to the cigarette, by-passes the tightly packed tobacco and hence the flow through the tightly packed tobacco is less than in the normal cigarette. Thus, because of the reduction in flow, the burning temperature is correspondingly lower. Further, because of the reduction in flow, the rate of oxidation is correspondingly reduced, together therefore, with the exothermic effects of the oxidation reaction. Moreover, because of the better heat conductivity provided by the tightly packed tobacco, the average maximum and idling temperatures are further reduced. Moreover the idling temperature is further reduced to the extent that the tightly packed tobacco interferes with convective flow.

Whether the column or columns are substantially vacant, or filled with loosely packed tobacco, the column or columns should not in total exceed /4 of the crosssectional area of the cigarette. If the cross-section of the column exceeds this area, in a cigarette where such column is originally vacant, the tobacco about such column, curling, migrating or falling thereinto will tend to burn hot due to the rapid flow of air down such column, causing, during smoking, a material quantity of tobacco burning at present cigarette temperatures, which situation, the cigarette of this invention is designed to avoid. If the column exceeds A of the cross-sectional area and is, in the construction of the cigarette, deliberately filled with loosely packed tobacco, then the risk of such tobacco burning at high temperatures, exist just as in the situation Where the tobacco has entered a vacant column space or spaces accidentally. It will, of course, be realized, that even with column cross-sectional areas, below those specified, some tobacco or the ends thereof in or bordering on a vacancy or loosely packed area, will tend to burn above the low temperatures for which the invention is designed; however, within the column cross-sectional area limits set out herein, the effects of loose tobacco in the column, will be negligible in amount. The column or columns of vacancy or low density provided in accord with the invention, must in total, be of sufficient area along the length of the tobacco to be smoked, to provide that the overall resistance to flow across the cigarette, including columns and tightly packed tobacco, is not more than the range for present cigarettes. The reason for this is that, while, on the one hand, overall flow resistance in the outer extent of a lesser amount than the range for present cigarettes, may be used to provide a cigarette of normal drawing qualities by compensating design in the inner extent thereof; on the other hand, a cigarette having, in its outer extent, a resistance to flow of higher than that of a normal cigarette cannot (within any material limits) by design of the inner extent, be made to assume the flow characteristics of a normal cigarette.

Preferably the column or columns are formed by inserting a metal shank or probe into the packed tobacco; or by having the shank in position prior to, and leaving it there during the packing, and withdrawing such probe after the construction of the cigarette, to tend to produce a passage in the cigarette. Tobacco may migrate or flex into such passage once formed, but the flow characteristics will approach relatively closely to that of an open bore and hence the resistance to flow in such passage will be much less than that of a conventional cigarette. The invention therefore includes a cigarette packed with tobacco to a higher density than conventional cigarettes, such tightly packed tobacco surrounding a central column wherein the tobacco is of lower density than conventional cigarettes.

The column of low density, must be surrounded by the packed tobacco, since, otherwise, if the column were bounded by the periphery of the tobacco and the paper, the paper would burn back ahead of the fireball on the tobacco and expose the end of the area of low density and the majority of the air would simply be drawn in by the user without passing through the fireball. In other words, if the column of low density is made peripheral relative to the tobacco, although inside the paper, then most of the air will by-pass the burning tobacco and the user receive an exceedingly diluted smoke, which would in fact be unsatisfactory.

In one form of the invention, the idling temperature of the tightly packed tobacco is further decreased by using tobacco shreds or fragments in larger than the normal size for cigarettes, in fact, of the size of pipe tobacco whereby the surface to volume ratio is reduced, and hence the smoking and idling temperature is lower. In most contemplated applications of the invention normal cigarette tobacco will be used. In accord with the invention there has been provided a cigarette wherein the oxidation and the temperature during idling and during pufiing have been reduced, and hence the cigarette is more healthful to the user, but wherein the novel cigarette in its drawing and idling qualities is not distinguishable from the present cigarette; and which can be designed to have a milder and more pleasant flavour than a conventional cigarette. It has further been noted that the cigarette constructed in accord with the invention has a 100% longer idling time than the conventional cigarette per unit weight of tobacco, giving evidence of the improved low temperature combustion characteristics.

Although the existence of a column of lower density or a passage through the tobacco would seem to imply dilution of the smoke received by the user, the tobacco at the fireball, in the process of burning, has been found to shrivel and bend, closing the end of the passage at the fireball and reducing the dilution to an amount not noticeable to the smoker.

The amount of packing of cigarette tobacco is measured in terms of its resistance to gas flow. In this application the resistance to flow is defined by reference to the pressure drop measured in centimeters of water per centimeter of tobacco in the direction of flow along the flow path; divided by the volume How in liters per second (per square centimeter of flow cross-section) of dry nitrogen at 80 F. and since the resistance so measured will not vary linearly with flow, the value given is the resistance measured to the flow created by a head of 0.3 centimeter of water per centimeter of length along the flow path.

In these units, conventional cigarettes have been found to range from a flow resistance of 30.4 to a flow resistance of 15.2.

In accord with the invention, the novel cigarette contains an outer extent of tobacco packed to a greater density than conventional U.S. cigarettes, surrounding a column (which may be vacant or may be all or partially filled with tobacco) of less density than that of the conventional cigarette. The column cross-sectional area and density in the column is of a value that the resistance to flow of the packed tobacco, surrounding the column of lower density, should be at least two and a half times the resistance to How of a conventional U.S. cigarette. Thus the column will have a resistance to flow of less than the more densely packed of US. cigarettes in order to bring the flow resistance of the outer extent within or below the fiow resistance range of a normal U.S. cigarette. In terms of the units discussed in preceding paragraphs, the tobacco should be packed about the column of lower density to an extent to have a resistance of from 80 units to 2,000 units with the preferred value being about 240 units. It should be explained that the density does not increase as fast as the units used and hence the range of densities corresponding to the range of flow resistance between 80 units and 2,000 units is not of as large an order. It will be realized that as the packing is increased beyond 240 units, the problem of adjusting the central area of reduced density and the impedance at the oral end of the cigarette, to produce the overall drawing qualities of a conventional cigarette, are increased. Packing to flow resistances higher than about 240 units will, varying with the value of the resistance of the unit, tend to increase the difliculty of having the cigarette stay alight during idling, and will tend to increase the amount of dilution of the smoke during puffing. The useful function of the device as a cigarette, having regard to idling and dilution, ceases at 2,000 units.

In drawings which illustrate a preferred embodiment of the invention:

FIGURE 1 is a cross-section of a cigarette taken on a plane cutting its longitudinal axis; and

FIGURE 2 is a view along lines 22 of FIGURE 1.

In the drawings a cigarette is provided extending from a free end, having a fireball F, to an oral end 0; and having: an outer extent of dimension E consisting of tobacco tightly packed to have a resistance of about 240 in the flow resistance units already defined, having a column 12 extending through such tobacco along the outer extent; and an inner and usually shorter extent 14, being preferably a filter. The filter 14 and the tobacco are surrounded by an open ended combustible casing 16 preferably of paper and preferably of conventional form. The paper cylinder may be replaced by casing of other combustible casing material.

In the preferred form of the invention, the cigarette with tobacco, paper and filter is made in the normal manner, with the tobacco being of a density, such, that when the central passage is provided as hereinafter described, the desired specific resistance of the tobacco sur rounding the passage will be in accord with the inventive concept. When the cigarette has been so constructed then a metal probe or shank is inserted through the tobacco along the length of the outer extent to provide a substantially empty column surrounded by the tobacco. The quantity of tobacco inserted in the paper before the probe or shank would be such that. after insertion of the probe or shank, the tobacco is packed to a resistance of about- 240 units.

Alternatively, the metal probe could be located in the cigarette at the time of construction, if convenient, and the tobacco packed therearound between the probe and the paper to the desired resistance, and the probe then Withdrawn.

It will be realized that, after withdrawal of the probe, some tobacco will leave the walls of the passage and curl or migrate into the passage, but this is considered within the scope of the invention, since the central portion will still form a column of much reduced density to counterbalance the resistance to flow, of smoke coming through the tobacco from the fireball.

It will also be realized that, if desired, the central passage may be made in one of the two methods set out above and filled with tobacco of low density so that in fact there is a low flow resistance column down the cigarette surrounded by tobacco with the low flow resi'stancy sufiicient to counter-balance the effects on flow, of the tightly packed tobacco, and arranged in conjunction with the inner extent of the cigarette, to provide overall flow characteristics equivalent to those of a conventional cigarette.

As previously explained, in order that the overall flow resistance qualities of the whole cigarette be equivalent to those of a conventional cigarette, the overall flow resistance qualities of the outer extent must be not greater than those of a conventional cigarette.

In accord with the invention, the tobacco surrounding the central passage or column of low density, is packed to an extent where the specific resistance to gas flow is greater than units, preferably of about 240 units and not exceeding 2,000 units. A filter or other flow impedance device suitable to form the oral end of a cigarette is then provided, and its flow characteristics are designed so that the overall flow characteristics of the cigarette are equivalent to a conventional cigarette. Preferably, therefore, the filter or oral end flow impedance, will be designed to give the novel cigarette a resistance of 15.2 to 30.4 (including in such calculation, the length of the filter or oral end flow impedance in measuring the overall length of the cigarette).

We claim:

1. A cigarette extending longitudinally between an oral and a free end, comprising: an outer extent of said cigarette extending inwardly from said free end, being a combustible casing packed with cut tobacco to a density to have a specific resistance to the flow of dry nitrogen at 80 F. (at the flow created by 0.3 centimeter of water per centimeter along the flow path) of from 80 to 2000 units, where such units are measured in amounts of pressure drop (measured in centimeters of H 0) per centimeter along the flow path volume fiow in litres per second (per square centimeter of flow cross-section) i at least one column longitudinally extending along said outer extent and bounded transversely by said packed tobacco, said longitudinally extending column being packed to a substantially lesser extent than said 80 units, and the area of said at least one column in a plane transverse to the longitudinal direction being not more than A of the corresponding area of the cigarette; and an inner extent of said cigarette between said oral end and said outer extent having a resistance to flow designed with said outer extent to provide an overall resistance to flow in the cigarette of 15.2 to 30.4 of the same units,

2. A cigarette as claimed in claim 1 wherein said column is packed to a density of less than 30.4 of said units.

3. A cigarette as claimed in claim 2 wherein said inner extent is a filter.

4. A cigarette extending longitudinally between an oral and a free end, comprising: an outer extent of said cigarette extending inwardly from said free end being a combustible casing packed with cut tobacco to an extent to have a resistance to the flow of dry nitrogen at 80 F. (at the flow created by 0.3 centimeter of water per centimeter along the flow path) of from 80 to 2000 units where such units are measured in:

pressure drop (measured in centimeters of H per centimeter along the flow path at least one column longitudinally extending along said outer extent and surrounded, when viewed longitudinally along said cigarette, by said packed tobacco, said at least one column being formed by a shank located in and extending along said outer extent when said tobacco has been packed, said shank being afterward withdrawn, and the area of said at least one column in a plane transverse to the longitudinal direction being not more than A the corresponding area of the cigarette; and an inner extent of said cigarette between said oral end and said outer extent, having a resistance to flow designed with said outer extent, to provide in the cigarette taken as a whole; a resistance to flow of 15.2 to 30.4 of said units.

5. A cigarette extending longitudinally between an oral and a free end, comprising: an outer extent of said cigarette extending inwardly from said free end, being a combustible casing packed with cut tobacco to an extent to have a resistance to the flow of dry nitrogen at 80 F. (at the flow created by 0.3 centimeter of water per centimeter along the flow path) of from 80 to 2000 units where such units are measured in:

pressure drop (measured in centimeters of H 0) per centimeter along the flow path a passage extending along said outer extent, surrounded, when viewed longitudinally along said cigarette, by such packed tobacco, said passage having an area, in a plane transverse to the longitudinal direction of not more than A the corresponding area of the cigarette.

6. A cigarette extending longitudinally between an oral and a free end, comprising: an outer extent of said cigarette extending inwardly from said free end, being a combustible casing packed with cut tobacco to a density to have a resistance to the flow of dry nitrogen at 80 F. (at the flow created by 0.3 centimeter of water per centimeter along the flow path) of from 80 to 2000 units where such units are measured in:

pressure drop (measured in centimeters of H 0) per centimeter along the flow path volume flow in litres per second (per square centimeter of flow cross-section) O o of less than 30.4 of said units, and said column having an area, in a plane transverse to the longitudinal direction being not more than /4 the corresponding area of the cigarette.

7. A cigarette as claimed in claim 6 having: an inner extent of said cigarette between said oral and said outer extent having a resistance to flow, designed with the design of said column to provide in the cigarette, taken as a whole, a resistance to flow, of 15.2 to 30.4 of the same units.

8. A cigarette extending longitudinally between an oral and a free end, comprising: an outer extent of said cigarette extending inwardly from said free end being a combustible casing packed with cut tobacco to an extent to have a resistance to the flow of dry nitrogen, at F. (at the flow created by 0.3 centimeter of water per centimeter along the flow path), of from 80 to 2000 units where such units are measured in:

at least one longitudinally extending column extending along said outer extent and surrounded, when viewed longitudinally along said cigarette, by said packed tobacco, said at least one column being formed by a shank located in said packed tobacco and extending along said outer extent and afterward withdrawn; said at least one column having an area, in a plane transverse to the longitudinal direction, being not more than A the corresponding area of the cigarette; an extent of said cigarette between said oral end and said outer extent having a resistance to flow, designed to provide in the cigarette, taken as a whole, a resistance to flow, of 15.2 to 30.4 of the same units.

9. A cigarette extending longitudinally between an oral and a free end, comprising: an outer extent of said cigarette extending inwardly from said free end, being a combustible casing packed with cut tobacco to an extent to have a resistance to the flow of dry nitrogen at 80 F. (at the flow created at 0.3 centimeter of water per centimeter along the flow path) of from 80 to 2000 units where such units are measured in:

pressure drop (measured in centimeters of R 0) per centimeter along the flow path at least one passage extending along said outer extent surrounded, when viewed longitudinally along said cigarette, by said packed tobacco; said at least one passage having an area, in a plane transverse to the longitudinal direction being not more than /4 the corresponding area of the cigarette; and an extent of said cigarette between said oral end and said outer extent having a resistance to flow, designed to provide in the cigarette an overall resistance to fiow, of 15.2 to 30.4 of the same units.

10. A cigarette as claimed in claim 1 wherein said inner extent is a filter.

11. A cigarette as claimed in claim 4 wherein said inner extent is a filter.

12. A cigarette as claimed in claim 1 wherein said tobacco is provided in particles of a size as used in pipe tobacco.

13. A cigarette as claimed in claim 4 wherein said tobacco is provided in particles of a size as used in pipe tobacco.

14. A cigarette as claimed in claim 5 wherein said tobacco is provided in particles of a size as used in pipe tobacco.

15. A cigarette as claimed in claim 1 wherein the tobacco about said at least one column is packed to an extent to have a resistance of about 240 of said units.

9 16. A cigarette as claimed in claim 4 wherein the tobacco about said at least one column is packed to an extent to have a resistance of about 240 of said units.

17. A cigarette as claimed in claim 5 wherein the tobacco about said passage is packed to an extent to have a resistance of about 240 of said units.

References Cited UNITED STATES PATENTS Willis 131-4 Hohn 131-13 X Helm 131-8 Boothroyd 131-66 Oster 131-8 ALDRICH F. MEDBERY, Primary Examiner. SAMUEL KOREN, Examiner. 10 H. P. DEELEY, Assistant Examiner.

Claims

9. A CIGARETTE EXTENDING LONGITUDINALLY BETWEEN AN ORAL AND A FREE END, COMPRISING: AN OUTER EXTENT OF SAID CIGARETTE EXTENDING INWARDLY FROM SAID FREE END, BEING A COMBUSTIBLE CASING PACKED WITH CUT TOBACCO TO AN EXTENT TO HAVE A RESISTANCE TO THE FLOW OF DRY NITROGEN AT 80*F. (AT THE FLOW CREATED AT 0.3 CENTIMETER OF WATER PER CENTIMETER ALONG THE FLOW PATH) OF FROM 80 TO 2000 UNITS WHERE SUCH UNITS ARE MEASURED IN: