U.S. patent number 3,910,287 [Application Number 05/126,122] was granted by the patent office on 1975-10-07 for smoking device.
Invention is credited to Richard R. Walton.
United States Patent |
3,910,287 |
Walton |
October 7, 1975 |
Smoking device
Abstract
A smoking device, preferably in the form of a cigarette, has an
inner lengthwise extending combustion zone and an outer combustion
zone surrounding it and separated from it by a barrier, both zones
containing particulate tobacco or the like. The inner zones
comprises the major volume of the device and is blocked off at the
mouthpiece end and the parts are arranged so that smoke from the
burning end portion of tobacco in the blocked off zone is by-passed
to the mouthpiece end through the other, minor volume, zone so that
the products of combustion are not deposited and reburned in the
first zone.
Inventors: |
Walton; Richard R. (Boston,
MA) |
Family
ID: |
22423098 |
Appl.
No.: |
05/126,122 |
Filed: |
March 19, 1971 |
Current U.S.
Class: |
131/336; 131/339;
131/360 |
Current CPC
Class: |
A24D
1/00 (20130101); A24D 1/04 (20130101) |
Current International
Class: |
A24D
1/00 (20060101); A24D 1/04 (20060101); A24D
001/06 () |
Field of
Search: |
;131/8,8A,9,1A,1R,15B,10.5,10.7,261B |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
1,914,963 |
|
Oct 1970 |
|
DT |
|
6,807,212 |
|
Nov 1969 |
|
NL |
|
401,174 |
|
Nov 1933 |
|
GB |
|
431,169 |
|
Aug 1967 |
|
CH |
|
Primary Examiner: Michell; Robert W.
Assistant Examiner: Pitrelli; John F.
Claims
What is claimed is:
1. In a smoking device having an ignition end and a mouthpiece end
and including an outer wrapper surrounding an elongated main charge
of smoking material, an annular passage defined in part by said
outer wrapper to conduct smoke from the burning cone of material
directly to the mouthpiece end by-passing the main charge, and
control means for limiting the passage of main-stream smoke from
the cone through the main charge to the mouthpiece end, the
improvement which comprises
means for supporting said outer wrapper at a plurality of spaced
areas in such predetermined spaced relationship in transverse
direction to the main charge that drawing on the device will cause
flame transfer between the main charge and the outer wrapper, carry
by-pass smoke through the passage to the mouthpiece end and at the
same time hold the outer wrapper against collapsing onto the charge
to pinch off the passage,
the outer wrapper being composed of combustible material having a
slower burning rate than that of the main charge so that the
burning rim of the outer wrapper will extend outwardly at least as
far as the burning cone of the charge as smoking progresses such
that smoke substantially to the exclusion of ambient air will be
drawn down the passage on each draught by the smoker, and
the mutual spacing of said supporting means being uniform and
close, whereby the running of the flame down the wrapper is
prevented.
2. The device of claim 1 including a mouthpiece affixed to the
mouthpiece end of the device and wherein smoke impermeable means in
said mouthpiece comprises said control means.
3. The device of claim 1 including a filter affixed to the
mouthpiece end of said device, at least a portion of the surface of
said filter being resistant to passage of smoke and comprising said
control means.
4. The device of claim 1 including a filter affixed to the
mouthpiece end of said device by means of tipping paper at least a
portion of the end of said filter which is adjacent the remainder
of said device being resistant to passage of smoke and comprising
said control means, another portion of the periphery of said filter
being permeable to smoke, and the tipping paper being spaced from
the permeable portion of the filter to provide a passage for
by-pass smoke to said permeable portion.
5. The device of claim 1 wherein said control means is arranged to
permit a predetermined percentage of mainstream smoke to pass to
the mouthpiece end of the device to mix with the by-pass smoke.
6. The device of claim 1 wherein said control means is arranged to
permit a predetermined percentage of mainstream smoke to pass to
the mouthpiece end.
7. The device of claim 1 wherein the outer surface of the main
charge is provided with longitudinally extending corrugations to
provide ribs which comprise at least in part said supporting
means.
8. The device of claim 1 wherein said main charge comprises a
tobacco product surrounded by an inner wrapper whose outer surface
with the inner surface of said outer wrapper defines said passage,
and wherein the means for supporting said outer wrapper includes a
minor charge of smoking material held within said passage between
said wrappers.
9. The device of claim 8 wherein the inner wrapper is in the form
of a cartridge, closed at least at its mouthpiece end, the closed
portion thereof comprising said control means.
10. The device of claim 8 wherein said inner wrapper is provided
with perforations near the ignition end of the device to facilitate
lighting.
11. The device of claim 8 wherein the inner wrapper is shorter than
the outer wrapper and has its ignition end spaced inwardly of the
ignition end of the device, the space between its end and the
adjacent ignition end of the device being filled with tobacco to
facilitate lighting and enhance the flavor of the first puffs.
12. The device of claim 8 wherein the combustible material in the
zone between said wrappers comprises portions of at least one of
said wrappers.
13. A smoking device for by-pass smoking having an ignition end and
a mouthpiece end, comprising
inner and outer wrappers of suitable combustible material,
the inner wrapper defining within itself a principal combustion
zone comprising a major volume of the device and the two wrappers
defining between them a secondary combustion zone comprising a
minor volume of the device,
tobacco essentially filling each zone, and
smoke obstructing means associated with the mouthpiece end of said
principal combustion zone for limiting the percentage of mainstream
smoke with will pass therethrough to the mouthpiece end of the
device,
the mutual transverse spacing and burning rates of the two wrappers
and the density and combustibility of the tobacco which separates
them being so chosen that as smoking progresses the burning portion
of the tobacco in said secondary zone maintains a predetermined
longitudinal relationship with the burning cone of tobacco in said
principal zone, so that when the smoker draws on the device at
least some air currents caused by the draught will pass through
said burning cone and will carry smoke therefrom into and through
said secondary zone, by-passing said principal zone, to the
mouthpiece end of the device.
Description
My invention relates to smoking devices, such as cigarettes,
cigars, and the like, but finds its greatest usefulness as a
cigarette which provides palatible smoke containing only a
controlled percentage of products of combustion deposited and
reburned and redeposited and reburned in the tobacco as smoking
proceeds.
For convenience in the specification and claims, the following
terms have the meanings indicated:
"Tabacco" means finely cut tobacco or shredded reconstituted
tobacco or other suitable particulate smoking material.
"Palatable smoke" means products of combustion acceptable to
smokers, whether it be from tobacco or cigarette paper or other
combustible components of the smoking device.
"Mainstream smoke" means smoke which is drawn from the lighted end
portion of a charge of tobacco through that same tobacco, thereby
depositing for reburning products of combustion therein. Mainstream
smoke also usually contains at least some very unpalatable and even
noxious smoke given off by the tobacco immediately adjacent the
burning cone which has been sufficiently heated to smolder but is
not yet burning, perhaps due to lack of oxygen more than lack of
heat--resembling that given off by an insufficiently ventilated
pile of damp burning leaves.
"By-pass smoke" means smoke which is drawn from the lighted end of
a charge of tobacco through a separate channel, by-passing such
charge of tobacco, so that such depositing and reburning are
reduced.
Modern cigarette technology has concentrated its efforts on
reducing undesirable substances in tobacco smoke reaching the
smoker primarily by providing filters of various sorts, although a
smoking device has also been suggested wherein the smoke from the
lighted end can by-pass the unburned tobacco through an open
central tube thus apparently reducing the depositing and reburning
problem but at the same time creating a serious risk of flame and
excessive heat reaching the smoker's mouth. Another approach which
has been taken is to treat the cigarette paper in such a way that
as smoking progresses toward the mouthpiece end the wrapper becomes
more porous, thereby increasing the amount of air introduced to
dilute the main stream smoke. This merely dilutes the smoke but
does not reduce or eliminate undesirable substances already
entrained therein.
The object of the present invention is the provision of an improved
smoking device for by-pass smoking wherein the percentages of
by-pass smoke and mainstream smoke can be controlled, the latter
being virtually eliminated if desired, which will have drawing and
burning characteristics closely approximating conventional smoking
devices, which will not have a tendency to extinguish itself
between puffs, and wherein the risk of flame and/or excessively hot
gases running from the burning end through an unobstructed space
toward the mouthpiece end is eliminated.
The invention features a device for by-pass smoking having an
ignition end and a mouthpiece end, the device comprising a material
holding wrapper defining a longitudinally extending space within
itself. Within the space and extending essentially throughout the
same is material at least some of which is combustible and capable
of giving off palatable smoke when burned, the material including
longitudinally extending barrier means dividing the space into
inner and outer combustion zones. Control means are provided for
controlling the percentage of mainstream smoke which can pass from
the burning portion of the material in one zone through such zone
to the mouthpiece end and means are provided for maintaining a
predetermined spaced relationship between the burning portions of
the material in both zones as smoking progresses so that when the
smoker draws on the device at least some air currents caused by the
draught will pass through the burning portion of the combustible
material in one zone and carry smoke therefrom into and through the
other zone, by-passing the said one zone, to the mouthpiece end of
the device.
In preferred embodiments the first named wrapper is of combustible
material, the material providing the longitudinally extending
barrier which divides the interior space into two combustion zones
comprises an inner wrapper of combustible material, the control
means comprises an obstruction at the mouthpiece end of the zone
through which the passage of mainstream smoke is to be controlled,
and the means for maintaining the predetermined spaced relationship
between the burning portions of the combustible material in each
zone includes the combustible material between the inner and outer
wrappers which material may be tobacco or portions of either or
both wrappers, such as longitudinally extending closely spaced ribs
formed thereon. The zone within the inner wrapper comprises a major
volume of the device and the zone between the wrappers comprises a
minor volume of the device and forms a channel for by-pass smoke
from the burning end of the material in the other zone to the
mouthpiece end.
In all forms of the invention I may provide either a mouthpiece or
a filter attached to the mouthpiece end arranged so that by-pass
smoke will pass through it to the mouth of the smoker. The barrier
to the passage of mainstream smoke may be smoke obstructing means
within the mouthpiece or, in the case of a filter, a portion of the
filter surface which is made resistive of impermeable to the
passage of smoke.
In those forms of the invention where a mouthpiece or filter is
employed the same may be affixed to the remainder of the device by
tipping paper, and the latter arranged to conduct by-pass smoke
from the by-pass channel to the interior of the mouthpiece, or, in
the case of a filter, to a smoke permeable portion of the filter.
In the case of the filter a smoke resistant or smoke impermeable
portion of the filter surface acts as the obstruction to passage of
mainstream smoke.
I prefer to employ in both combustion zones of the device a
particulate combustible material which may comprise finely cut
tobacco or shredded reconstituted tobacco. In one form of the
invention such particulate tobacco material fills the zone which
comprises the major volume of the device and portions of one or
both wrappers essentially fill the other zone. In still another
form of the invention the wrapper which defines the inner
combustion zone and major volume of the device is in the form of a
cartridge filled with tobacco, closed at least at its mouthpiece
end, the closed portion thereof comprising the obstruction to the
passage of mainstream smoke to the mouthpiece end.
In all forms of the invention, optionally, I may arrange the
obstruction to permit a predetermined percentage of mainstream
smoke to pass the mouthpiece end of the device to mix with the
by-pass smoke.
A presently preferred embodiment employs inner and outer wrappers
of cigarette paper or reconstituted tobacco, with the space within
the inner wrapper defining the major volume of the device and the
principal combustion zone, while the space between the wrappers
defines a minor volume and the secondary combustion zone. Tobacco
fills both zones. An obstruction blocks all or a desired portion of
the mouthpiece end of the principal combustion zone. The mutual
spacing and burning rates of the two wrappers and the density and
combustibility of the tobacco are so chosen that as smoking
progresses the burning portion of the tobacco in the secondary zone
maintains a predetermined relationship with the burning cone of
tobacco in the principal combustion zone, so that when the smoker
draws on the device at least some air currents caused by the
draught will pass through the burning cone of tobacco in the
principal zone and will carry therefrom into and through the
secondary zone, by-passsing the principal zone, to the mouthpiece
end of the device.
At the ignition end of the device, optionally I provide
perforations in the inner wrapper to facilitate lighting. The inner
wrapper likewise may be made shorter than the outer wrapper, having
its end spaced inwardly from the end to be lighted, and the space
between its end and the adjacent end of the outer wrapper filled
with tobacco filler, both to facilitate lighting and to enhance the
flavor of the first puffs.
As an alternative to the use of only a partial obstruction to
provide both mainstream and by-pass smoke to the mouthpiece end, I
may provide an inner wrapper having longitudinal portions having a
higher burning rate than the remaining portions, so as to provide
gaps after the device is lighted through which some smoke from the
lighted end may pass, and thence be drawn through at least some
tobacco filter en route to the space between the wrappers from
where it passes on to the mouthpiece end.
The burning rates of the inner and outer wrappers are regulated in
a manner known in the art, as by using tobacco paper of different
thicknesses, density, or porosity, or the application of flame
accelerating or retarding materials thereto.
In the annexed drawings illustrating preferred embodiments of the
invention:
FIG. 1 is a partially broken away perspective view of a cigarette
according to the invention;
FIG. 2 is a similar view of an alternative construction;
FIG. 3 is an enlarged section of a portion of another form of a
cigarette taken through the longitudinal axis;
FIG. 4 is a section on line 4--4 of FIG. 3;
FIG. 5 is a longitudinal sectional view of a further modified
form;
FIG. 6 is a longitudinal section on an enlarged scale of the
ignited end of the cigarette of FIG, 5 showing by arrows the air
and smoke flow paths;
FIG. 7 is a view similar to FIG. 6 but on a smaller scale of
another embodiment;
FIG. 8 is a view similar to FIG. 3 of a cigarette employing a
filter at the mouthpiece end;
FIG. 9 is an exploded view of still another form of filter
cigarette;
FIG. 10 is a section on an enlarged scale of the filter end of the
device of FIG. 9;
FIG. 11 is a view similar to FIG. 9 of still another
modification;
FIG. 12 is a view similar to FIG. 10 of the device of FIG. 11;
FIG. 13 is an exploded view partly in longitudinal section of still
a further modified cigarette employing a disc having a flexible
peripheral portion as the obstructing means; and,
FIG. 14 is an enlarged sectional view of a portion of the assembled
cigarette of FIG. 13.
As shown in FIG. 1, a cigarette for by-pass smoking according to
the invention includes combustible smoking material such as tobacco
10 and a conventional outer wrapper 12 of cigarette paper. Disposed
within the outer wrapper 12 is an inner wrapper 14 which encloses
the tobacco filler 10. The mouthpiece end of the inner wrapper 14
is sealed off as at 16 by wax or other suitable material to provide
an obstruction or barrier which limits, or completely prevents, the
passage of mainstream smoke therethrough. A member 18, having
perforations 20 therein, is provided to separate the main portion
of the cigarette from the mouthpiece itself 22 which is held to the
cigarette proper by tipping paper 44. The mouthpiece 22 may or may
not include a filter medium such as is well known in the art.
Combustible material yielding palatable smoke forms spacing means
24 between the outer and inner wrappers. While the medium 24 may be
chosen from a broad range of materials I prefer a discontinuous
combustible material of a "pebbly" or "grainy" nature, such as
shredded tobacco or reconstituted tobacco, so as to provide
virtually continuous support for the outer wrapper while at the
same time to provide a passage for by-pass smoke longitudinally
along the annular channel between the inner and outer wrappers. For
example, particulate matter, such as shredded reconstituted tobacco
(RTP), may be adhered to the outer surface of the inner wrapper or
to the inner surface of the outer wrapper as the elements are
assembled.
The inner wrapper 14 may, if desired, be provided with perforations
26 near its outer or ignition end 28. The perforations 26 have been
found to be desirable to increase the air flow through the tobacco
10 itself at the instant of lighting, thereby to make the cigarette
easier to light.
Alternatively, the inner wrapper 14d may be somewhat shorter than
the outer wrapper 12d so that end 28d is withdrawn into the body of
the cigarette, as shown in FIG. 7. This structure also provides
improved lighting characteristics and may enhance the flavor of the
first few puffs because of the presence of the extra tobacco 60 at
the outer end.
FIG. 2 illustrates a cigarette construction having a recessed inner
wrapper 14a, provided with a multitude of longitudinally extending
corrugations forming the combustible spacing medium in the by-pass
channel. The spaces between the outer wrapper 12 and the "valleys"
32 of the outward-facing corrugations of inner wrapper 14a provide
a direct route for by-pass smoke from the burning end of the
cigarette to reach the smoker without passing through the unburned
tobacco 10 within the inner wrapper. It is thus apparent that the
means for maintaining the separation of the inner and outer
wrappers may simply be the numerous ridges or "hills" of
corrugations on the inner wrapper. Alternatively, the inner wrapper
could be embossed upon only its outer surface or a separate
corrugated or embossed layer of material (e.g., RTP) could be
disposed between smooth inner and outer wrappers. In all cases the
support given to the outer wrapper by its contact with the surface
of the supporting medium must be sufficiently uniform to prevent
undesirable running of flame down the outer wrap.
FIGS. 3 and 4 show another variation in which the inner wrap 14a is
similar to that in FIG 2, that is fluted to provide the support for
the outer wrapper, and employing a filter. The filter 22b has a
sealing projection 48 and the by-pass smoke passes through a
pervious annular portion of the filter as indicated by the arrow 47
in FIG. 3. The parts are held together by tipping paper 44. Opening
49 permits a predetermined portion of mainstream smoke to enter the
filter and blend with the by-pass smoke.
FIG. 5 illustrates a cigarette construction similar to that of FIG.
1 but including simplifications which are presently thought to make
the manufacture of the cigarette more compatible with existing
cigarette making machinery. Once again tobacco 10 is disposed
within an inner wrapper 14c. An outer wrapper 12 is separated from
the inner wrapper 14 by a medium 24, which is preferably finely cut
tobacco or reconstituted tobacco particles as in FIG. 1. In place
of the sealed end 16 of inner wrapper 14 and perforated barrier 18
as in FIGS. 1 and 2, a plug 34 is disposed in mouthpiece 22c
adjacent the open end 20a of the inner wrapper. The mouthpiece is
attached by means of tipping paper 44. The plug may be of any
material which is impervious to the smoke of burning tobacco. The
plug 34 may, if desired, obstruct less than the entire
cross-sectional area of the open end 20a of the inner wrapper. A
convenient way to achieve this is to make the plug 34 in
cylindrical form with its axis aligned with that of the cylindrical
inner wrapper 14, but having a diameter less than that of the
wrapper 14. In this a predetermined percentage of mainstream smoke
may be blended with by-pass smoke.
The plug 34 may be maintained in the correct orientation within the
mouthpiece 22 by means of a plurality of radially extending fins 35
which contact the cylindrical mouthpiece 22c.
FIG. 6 shows the flow-paths which the air and smoke are believed to
follow at the lighted end of the novel smoking device of the
embodiments just described from which illustration the principle of
operation of the invention becomes apparent. When the smoker draws
on the cigarette, a current of air is drawn through the space
between the wrappers. If the outer end of the outer wrapper extends
at least as far as the burning cone of tobacco, this draught will
produce air flow through the burning cone 10a and into the by-pass
space between the wrappers, as shown by the arrows. This causes the
cone and adjacent wrappers and spacing medium 24 to glow. Smoke
produced by the cone 10a by-passes the tobacco filler 10 and flows
through the space between the wrappers to the mouthpiece end of the
cigarette. It is clear that the presence of this
outwardly-extending portion of the outer wrapper is essential to
the functioning of the cigarette; but for it no air currents would
be set up by drawing on the cigarette which would influence the
burning of the cone. Stated in another way, if the entrance to the
passage between the wrappers is too remote from the flame, a
draught set up therein will neither cause burning nor pull any
smoke into the by-pass channel between the wrappers.
To achieve this desired projection of the end of the outer wrapper
to at least partially surround the burning cone of tobacco, it is
necessary to select its "burning rate" as less than that of the
inner wrapper. By this is meant not necessarily the relative
burning rates of the materials in open air, but their effective
burning rates in the environment of the particular cigarette
construction. Thus the effective burning rate of the outer wrapper
is affected by its proximity to the inner wrapper as well as by the
nature, including combustibility, and compactness, of the
combustible materials 10 and 24. The proximity of the outer wrapper
to the inner wrapper is not merely a function of relative initial
diameters, but also may change as the cigarette is smoked because
of pressure differential induced by the smoker's drawing on the
cigarette. This effect is subject to a number of variables,
including original spacing from the inner wrapper, permeability and
stiffness of the wrapper, and the support afforded by the spacing
medium. It may be said, generally, that the closer the outer
wrapper is to the inner wrapper, the more nearly they will burn at
the same speed in spite of different absolute burning rates. On the
other hand, the channel between them must remain sufficiently open
always to permit the passage of the by-pass smoke with the desired
pressure drop. However, the support afforded the outer wrapper must
be substantially continuous, for the flame will travel undesirably
down any unsupported area of the outer wrapper. Having in mind the
teachings of the invention, the skilled cigarette maker will be
able to achieve a nice balancing of the relevant factors so as to
produce a satisfactory cigarette for by-pass smoking according to
the invention.
In FIG. 8 there is shown still another embodiment. In this case the
filter 22d is heat-sealed at 46 to provide a smoke impermeable
barrier. Its cylindrical outer surface however is porous, and may
be smoke permeable paper. The tipping paper 44e is embossed. This
form of the invention depends for its success on the fact that the
filter will be imperfectly sealed against the inner end of the
outer wrapper 12e. Drawing on the cigarette will produce quite
sufficient leakage around the inner edge of the outer wrapper so
that by-pass smoke will travel, as shown by the arrows, out from
under the inner wrapper 14e, through channels provided by the
embossed tipping paper, and back in through the porous wall of the
filter 22d to the smoker's mouth. In this case the embossed tipping
paper is of course glued in sealing relation to the outer wrapper
only at its forward portion and to the surface of the filter at its
inner portion, as indicated at 54 and 56.
FIGS. 9 and 10 show two alternative structures for permitting
substantially only by-pass smoke to reach the filter 22f. The inner
end of the outer wrapper 12f is perforated as at 40 as is the outer
portion of the filter as at 42. An embossed tipping paper 44f
mounts the filter to the cigarette proper and it is sealed to the
wrapper 12f at its outer edge and to the filter along its inner
edge. By-pass smoke will pass out through the gap at the base of
outer wrapper 12f, along the passages inside the embossed tipping
paper and into the openings 42 as indicated by arrows. The forward
end 46f of the filter 22f is made impervious by heat sealing, as in
the embodiment of FIG. 8.
FIGS. 11 and 12 show still another embodiment wherein the filter
22g is provided with an outwardly projecting cylindrical portion 48
which is impervious to smoke. When the parts are assembled by
tipping paper 44g this portion is wedged into the tobacco in the
inner wrapper 14g and acts as a barrier to prevent mainstream smoke
from reaching the filter. By-pass smoke passes from between
wrappers 12g and 14g through permeable face 46g of filter 22g as
indicated by the arrows in FIG. 12.
FIGS. 13 and 14 show another variation wherein a filter 22h,
similar to that of FIG. 11, but with an arcuate permeable forward
surface 52, is assembled by tipping paper 44h to the main cigarette
comprising inner wrapper 14h, outer wrapper 12h, main tobacco
charge 10h and minor tobacco charge 24h. A smoke impermeable disc
50 of flexible material is interposed between the filter and the
cigarette and its outer rim will flex, when the smoker draws on the
cigarette, down into the channel produced by the portion 52, thus
permitting by-pass smoke, but not mainstream smoke, to pass through
the filter.
While by-pass smoke contains the lowest percentage of products of
repeated deposition and reburning of products of combustion, it is
clear nevertheless that substantial advantages of the invention are
still present if a predetermined portion of mainstream smoke is
allowed to mix with by-pass smoke. Furthermore, by varying the
percentage of the portion, the taste and drawing properties of the
cigarette may be tailored to satisfy a wide range of
preferences.
One way to adjust the relative percentages of mainstream and
by-pass smoke is to provide a partially pervious obstruction, such
as plug 34 in FIG. 5, for the cylinder of tobacco filler 10. This
may be accomplished in the embodiments of FIGS. 1 and 2 by making
the sealed end 16 of the inner wrapper only somewhat resistant to
the passage of smoke, thereby inducing the bulk of the smoke to
flow in the by-pass channel(s) at the periphery of the cigarette.
In the embodiment of FIG. 5, the diameter of the plug 34 may, as
already mentioned, simply be varied, instead of varing its
porosity.
As a second way to provide some mainstream smoke to the mouthpiece,
the inner wrapper, in the embodiments such as those of FIGS. 1 and
2, may be constructed to have longitudinal strips which burn at a
faster rate than the remainder of the inner wrapper to permit at
least a portion of the smoke to pass through some unburned tobacco.
Since the percentage of the total inner wrapper area which burns
faster may be varied, the amount of smoke which travels through the
tobacco may be adjusted to any taste. The faster burning strips may
be produced by treatment of the paper of the inner wrapper, by
embossing to provide thinner paper in those strips, or by any
conventional technique.
Examples of additives to tobacco paper which are used to influence
their burning rates are citrate salts to increase the rate of
phosphates to slow the rate. Also, the addition of inert materials
to the paper will slow the burning rate. More porous papers burn
more quickly; denser papers, more slowly.
While no exact limits can be stated because flame transfer between
inner and outer wraps depends not only on mutual spacing but also
on the nature, density, and burning rate of the media between and
within them, generally speaking I have found that utilizing
cigarette papers 0.001 inch thick for both inner and outer wrappers
in a FIG. 1 embodiment for example, and reconstituted tobacco
particles adhered to the outer surface of the inner wrap, excellent
results are obtained with a gap of about 0.0125 inch between inner
and outer wrappers. This cigarette had excellent drawing qualities.
It was noted that even after the cigarette was smoked all the way
down, the filter in the mouthpiece remained clean, in marked
contrast to the condition of a similar filter of an ordinary
filter-tip cigarette. The last puff was just like the first puff so
far as flavor, aroma, and quality were concerned. In contrast a
spacing of 0.030 inch appears to be too great, and in most cases
the cigarette would go out after lighting and could not be kept lit
even by drawing on it. This cigarette had poor drawing
qualities.
* * * * *