Note: Descriptions are shown in the official language in which they were submitted.
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SMOKING ARTICLE WITH NOVEL WRAPPER
FIELD OF THE DISCLOSURE
This disclosure relates generally to a smoking article and, more particularly,
a smoking article
having a pattern provided on the wrapping paper for reducing ignition
propensity of the burning
smoking article when left unattended upon a substrate.
SUMMARY
A smoking article includes a tobacco rod with a wrapper paper formed from a
base web having
a nominal permeability. Zones of add-on material are preferably applied to the
base web
according to a pattern that includes a plurality of circumferentially spaced
regions that are
io longitudinally spaced along the tobacco rod. Each of the regions
preferably includes at least
two substantially opposed zones of add-on material, which zones exhibit a
permeability less
than the nominal permeability. The zones of add-on material preferably have
sufficient size,
shape, and add-on material concentration that, when the tobacco rod is
smoldering and is
placed on a substrate, that the tobacco rod will tend to extinguish at the
corresponding region.
For each first, second, and third consecutive region, the zones of the second
region are
circumferentially offset from the zones of the first region. Moreover, the
zones of the third
region are circumferentially offset from the zones of both the first and
second regions.
The pattern preferably continues substantially along the tobacco rod so that,
when the
tobacco rod is placed on a substrate and viewed from an end, at least one
region will be
situated such that its zones of add-on material are positioned substantially
at side portions of
the tobacco rod.
The smoking article preferably exhibits an Ignition Propensity no greater than
about 25%
and a self-extinguishment value no greater than about 50%.
A smoking article according to this disclosure preferably includes a wrapper
paper
having a pattern formed by a permeability reducing film-forming compound. The
pattern is
selected so that when the smoking article is placed on a substrate, the
smoking article will self-
extinguish when an advancing burn line reaches one or more longitudinal
locations where film-
forming compound is present at sides of the smoking article not in contact
with a substrate but
those sides having film-forming compound or agent will not cause the smoking
article to self-
extinguish when the smoking article is held by a smoker. Hence, a pattern may
be selected that
takes into account the obstructed airflow through the side or side portion of
the smoking article
that contacts a substrate. By doing so, a smoking article may have both a
reduced ignition
propensity and satisfactory free-burn quality.
The smoking article may have a circular or near circular cross section,
implying that any
side or side portion of the smoking article may be placed against a substrate,
such as when the
smoking article is dropped on a surface or when the smoking article is left
unattended. In this
respect, the patterns described herein define sides or side portions having
film-forming
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2
compound not in contact with the substrate, regardless of the smoking article
orientation when it
happens to be in contact with the substrate. The smoking article may also have
a non-circular
cross-section.
The wrapping paper and its zones of add-on material may include a plurality of
discrete
shapes, each of which extends over less than the length of the tobacco rod. At
each of a
plurality of spaced-apart longitudinal locations along the tobacco rod, only a
first and second
shape of the pattern is present in a cross section taken substantially
perpendicular to the
longitudinal axis of the tobacco rod. At one such location, the first shape is
disposed only on a
first side of the smoking article and the second shape is disposed only on a
second side
io opposite the first side of the smoking article. The first and second
shapes may be spaced apart
by substantially 1800 and have a porosity substantially less than the porosity
of the base web. If
desired, the plurality of discrete shapes may be arranged so that a cross-
sectional plane
through the tobacco rod intersects at least two such discrete shapes.
BRIEF DESCRIPTION OF THE DRAWINGS
Many objects and advantages of the present disclosure will be apparent to
those skilled
in the art when this specification is read in conjunction with the
accompanying drawings,
wherein like reference numerals are applied to like elements and wherein:
FIG. 1 is a perspective view of a smoking article in accordance with a first
embodiment
zo of the invention.
FIG. 2 is an enlarged plan view of an unwrapped portion of wrapping paper used
in the
construction of the smoking article of FIG. 1.
FIG. 3 is an enlarged plan view of a wrapping paper for the smoking article
illustrating a
second quadrilateral pattern.
FIG. 4 is an enlarged plan view of a wrapping paper for the smoking article,
illustrating a
third quadrilateral pattern.
FIG. 5 is an enlarged plan view of a wrapping paper for the smoking article,
illustrating a
fourth quadrilateral pattern.
FIG. 6 is an enlarged plan view of a wrapping paper for the smoking article,
illustrating a
triangular pattern.
FIG. 7 is a side view of the smoking article using the wrapper paper of FIG. 3
with the
smoking article on a substrate and oriented so that a first side portion of
the smoking article
contacts a substrate.
FIG. 8 is a side view of the smoking using the wrapper paper of FIG. 3 with
the smoking
article on a substrate and oriented so that a second side portion of the
smoking article contacts
the substrate.
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3
FIG. 9 is a side view of the smoking article using the wrapper paper of FIG. 3
with the
smoking article on the substrate and oriented so that a third side portion of
the smoking article
contacts the substrate.
FIG. 10 is a cross-sectional view of the smoking article taken along line 10-
10 of FIG. 7.
FIG. 11 is a cross-sectional view of the smoking article taken along line 11-
11 of FIG. 7.
FIG. 12 is a cross-sectional view of the smoking article taken along line 12-
12 of FIG. 7.
FIG. 13 is an enlarged cross-sectional view of the smoking article positioned
on a
substrate and illustrating airflow to a smoldering coal.
FIG. 14 is an enlarged cross-sectional view of the smoking article removed
from the
io substrate and illustrating airflow to a smoldering coal.
DETAILED DESCRIPTION
In accordance with this description, a first embodiment of a smoking article
20 (see
FIG. 1) includes a tobacco rod 22. The tobacco rod 22 may include a cut filler
of tobacco and is
surrounded by wrapper paper 24. One end of the smoking article 20 may include
a suitable
filter 26 surrounded by suitable filter tipping paper 27. The smoking article
20 typically may
have a generally circular cross section over the length of the smoking
article. Nevertheless,
other cross-sectional shapes including, for example, oval, are within the
scope of this
description. The tobacco rod 22 has a nominal length L measured from an edge
of the tipping
paper 27 to the free end of the tobacco rod 22 along a longitudinal axis A of
smoking article 20.
By way of example, that nominal length may lie in the range of about 60mm to
about 100mm.
The wrapper paper 24 includes a base web which typically is permeable to air.
Permeability of wrapper paper is typically identified in Coresta units. A
Coresta unit measures
paper permeability in terms of volumetric flow rate (i.e., cm3/sec) per unit
area (L e., cm2) per unit
pressure drop (i.e., cm of water). The base web of conventional wrapper paper
also has well-
known basis weights, measured in grams per square meter, abbreviated as "gsm".
The
permeability and basis weight for the base web of typical smoking article
papers commonly
used in the industry are set out in the table below:
Permeability, Coresta units Basis Weight, gsm
24 25
33 25
46 25
60 26
For purposes of this description, the base web 24 of a preferred wrapper paper
has a
permeability of at least about 20 Coresta units. Most preferably, the wrapping
paper has a
permeability greater than about 30 Coresta, such as common base webs having
nominal
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4
permeabilities of about 33 and about 46 Coresta with a basis weight of about
25 gsm. For some
applications, the base web may have a permeability of greater than about 60
Coresta, or greater
than about 80 Coresta, or even higher permeability values.
With reference also to FIG. 2, the paper wrapper further comprises pairs of
add-on
material zones at spaced locations along the tobacco rod 22 in FIG. 1 (such as
the opposing
pair of zones 34d, 36d).
Each pair of rectangular zones (for example, 34a and 36a--the latter not being
visible in
FIG. 1) define a circumferential region 31 (for example, the region 31a). The
"width" of the
banded region 31a is measured from a leading edge 7 of the region 31a (it
being closest to an
io
approaching coal) to the trailing edge 9 (it being most remote from an
approaching coal).
Preferably the width of the regions, e.g., 31a, lies in the range of about
5.5mm to about 12mm,
more preferably, about 7mm to about 10mm, and most preferably about 8mm to
about 9mm.
Moreover, at each circumferential region, such as region 31a, the zones 34a
and 36a are
circumferentially spaced apart such that they are disposed in mutually
opposing relation along
opposite sides of the wrapper 24 when formed on a tobacco rod 22. Preferably
each zone 34a,
36a extends circumferentially (Le., in cross-measure relative to the paper
web) in the range of
about 5mm to about 9mm in cross-measure, more preferably, about 6mm to about
7mm in
cross-measure.
It is noted for sake of convention that, in describing dimensions of various
embodiments
herein, that "width" will extend in a longitudinal direction of the tobacco
rod, whereas a
dimension in the circumferential direction will be expressed as "transverse"
or "cross-direction"
or "cross-measure".
It is further noted that the area 33 of base web between adjacent regions 31a,
31b and
the areas between opposing zones within each region (such as between the
opposing zones
34b, 36b of the region 31b) are preferably essentially free of add-on material
comprising the
zones (e.g., zones 34b, 36b).
The longitudinal distance between adjacent regions (such as between regions
31a, 31b is
referenced as band spacing 33, which is preferably about 4mm to about 12mm,
and more
preferably about 6mm to about 8mm.
Preferably, the respective opposing zones 34, 36 of each region 31 are offset
from those
of a preceding row or region to a degree (in accordance with teachings which
follow) and a
sufficient number of regions 31 are established along a given tobacco rod (per
selection of
band-region width and width of band-region spacing) that, when the smoking
article is placed up
on a substrate, that there occurs at least one location 101along the tobacco
rod 22 where the
respective pair of zones 34 are oriented substantially alongside the tobacco
rod 22, such as the
opposing pair of zones 34b, 36b in FIG. 1. It is at or about this portion
(location 101) of the
tobacco rod 22 where self-extinguishment is most likely to occur. The location
along the
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tobacco rod 22 where this orientation most closely occurs is hereinafter
referenced as the
"oriented snuffer region 101."
Because the smoking article 26 might be laid upon a substrate differently from
that
shown in FIG. 1 and/or because its pattern of zones may differ, it is to be
realized that the
5 oriented snuffer region 101 may appear at different longitudinal
positions along the tobacco
rod 22 for different rotational positions of the tobacco rod 22. The pattern
of zones and the
band spacing 33 may be selected such that more than one oriented snuffer
region 101 may
occur along the tobacco rod 22.
Preferably, each zone 34, 36 and 36' includes sufficient add-on material to
reduce the
permeability of the wrapper at each zone to 0.0 to about 10 CORESTA, more
preferably about 7
Coresta or less.
For purposes of this description, a pattern of add-on material is applied to
the wrapper
paper 24 to obtain improved ignition propensity characteristics and also to
obtain improved self-
extinguishment characteristics. Ignition propensity is a standard test
conducted as set forth in
ASTM E 2187--04, "Standard Test Method for Measuring the Ignition Strength of
Smoking
articles".
Ignition propensity
measures the probability that a smoking article, when placed on a substrate,
will generate
sufficient heat to maintain static burning of the tobacco rod 22. Low values
for ignition
propensity are desirable as such values correlate with a reduced likelihood
that a smoldering
smoking article will cause combustion in an underlying substrate.
Self-extinguishment herein is a reference to smoldering characteristics of a
smoking
article under free-burn conditions. To evaluate self-extinguishment, a
laboratory test is
conducted at a temperature of 23 C 3 C and relative humidity of 55% 5%,
both of which
should be monitored by a recording hygrothermograph. Exhaust hood(s) remove
combustion
products formed during testing. Prior to testing, smoking articles to be
tested are conditioned at
55% 5% relative humidity and 23 C 3 C for 24 hours. Just prior to testing,
the smoking
articles are placed in glass beakers to assure free air access.
Self-extinguishment testing takes place within an enclosure or test box. A
single port
smoking machine or an electric lighter is used to ignite the smoking articles
for the test. During
testing, an apparatus or "angle holder" holds the smoking articles to be
tested by holding an end
at angles of 0 degrees (horizontal), 45 degrees, and/or 90 degrees (vertical).
Twenty (20)
smoking articles are tested at each of the 0 degrees, 45 degrees, and 90
degrees positions. If
more than one apparatus is used, the apparatuses are preferably positioned
such that the
smoking articles face away from each other to avoid cross interference. If a
smoking article
goes out before the front line of the smoldering coal reaches the tipping
paper, the outcome is
scored as "self-extinguishment"; on the other hand, if the smoking article
continues smoldering
until the front line of the smoldering coal reaches the tipping paper, then
the outcome is scored
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as "non-extinguishment". Thus, for example, a self-extinguishment value of 95%
indicates that
95% of the smoking articles tested exhibited self-extinguishment under free-
burn conditions;
while a self-extinguishment value of 20% indicates that only 20% of the
smoking articles tested
exhibited self-extinguishment under free-burn conditions.
The self-extinguishment value may be referred to in terms of "self-
extinguishment at 0 degrees
value", "self-extinguishment at 45 degrees value", or "self-extinguishment at
90 degrees value",
each of which refers to the value of self-extinguishment at the specified
tested angle. In
addition, the self-extinguishment value may be referred to in terms of "self-
extinguishment
Average value", which refers to an average of the three angular positions:
namely, an average
io
of (i) the "self-extinguishment at 0 degrees value", (ii) the "self-
extinguishment at 45 degrees
value", and (iii) the "self-extinguishment at 90 degrees value".
A reference to "self-
extinguishment value" or does not distinguish between self-extinguishment at 0
degrees, self-
extinguishment at 45 degrees, self-extinguishment at 90 degrees, or self-
extinguishment
average values and may refer to any one of them.
The phrases "self-extinguish under free-burn conditions" or "self-
extinguishment under
free-burn conditions" as used herein, refer to the extinguishment of a
smoldering cigarette
without puffing, when such cigarette is subjected or exposed to free-burn
conditions.
As presently understood, the staggered zones of add-on material according to
this
description permit a smoking article 20 (see FIG. 1) to be designed with an
advantageous
combination of low ignition propensity values and low self-extinguishment
values. The patterns
of low permeability zones of add-on material provide areas of film-forming
compound along the
length of the tobacco rod 22 that can cooperate with a substrate to extinguish
the lit smoking
article 20 when it is placed on that substrate, yet these areas of add-on
material (such as a film-
forming compound) cause the smoking article 20 to self-extinguish at
statistically fewer
occurrences when the smoking article 20 is held by a smoker in a free-burn
condition. Thus, the
smoking article 20 can exhibit a reduced ignition proclivity while retaining a
desirable free-burn
quality or low self-extinguishment value by applying a pattern 30 of film-
forming compound to
the base web according to this description.
To achieve desirable ignition propensity and self-extinguishment
characteristics of the
smoking article, a pattern 30 (see FIG. 2) is applied to the base web 24 of
the wrapper paper,
preferably while the base web 24 is in an unfolded condition, such as shown in
FIG. 2, or when
the base web comprises a roll of cigarette paper that has yet to be slit into
bobbins. An object of
this description is to provide wrapper papers which, when formed into a
tobacco rod 22, exhibit
IP values no greater than 25 and self-extinguishment values no greater than
50. Even more
preferred, is an IP value for the resulting smoking article no greater than
about 15; and the most
preferred IP value for the resulting smoking article is no greater than about
10. Lower self-
extinguishment values are also desired.
In this connection, a more preferred self-
_
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7
extinguishment value is less than about 25; while the most preferred self-
extinguishment value
is less than about 10.
Referring specifically to FIG. 2, the transverse dimensions of the wrapper
paper 24 are selected
based on the diameter of the finished smoking article (about 7mm to about
10mm) and allowing
for overlapping material at a longitudinal seam of about 1mm to about 2 mm.
For example,
allowing for 1mm overlapping seams, the wrapper-paper cross-web dimension may
be about
27mm for a smoking article having a circumference of about 25.6mm.
Preferably, the pattern is applied to the base web such that a plurality of
circumferentially
extending regions 31a, 31b, 31c, 31d (defined by broken lines in FIG. 2) are
disposed at spaced
io locations along the tobacco rod 22 (see arrow B, in FIG. 2). The add-on
material can be applied
to one or to both sides of the base web. Preferably, three to six, and most
preferably four to six
or more, of the regions 31 occur in the nominal length of the tobacco rod 22.
Each of the
circumferential regions 31a, 31b, 31c, 31d has a longitudinal pitch along the
tobacco rod 22
(i.e., length measured along the tobacco rod from the beginning of one region
to the beginning
of the adjacent region) which is less than the nominal length of the tobacco
rod 22. By selecting
the longitudinal pitch length at about 25% of the nominal length, four regions
will be provided on
each tobacco rod 22.
Within each circumferential region, e.g., 31a, at least two zones, e.g., 34a,
36a, of add-
on material are provided. Note that the zones of add-on material in all of the
Figures are
identified with stippling to aid identification of them; however, in a smoking
article or wrapper
paper for such a smoking article, these zones of add-on material may, or may
not, be visually
identifiable. Each of these zones is preferably spaced circumferentially such
that the zones will
be opposed to one another in the finished tobacco rod 22. Moreover, for each
triplet of zones,
e.g., 31a, 31b, 31c, the zones 34b, 36b of the second region 31b preferably
are
circumferentially offset from the zones 34a, 36a of the first region.
Furthermore, the zones 34c,
36c of the third region 31c preferably are circumferentially offset from the
zones 34b, 36b of the
second region 31b, and even further offset circumferentially form the zones
34a, 36a of the first
region 31a.
As depicted in FIG. 2, the add-on zones of each region in this embodiment are
laterally offset in
a circumferential direction from the add-on zones of an adjacent region by a
distance that is a
function of the transverse dimension of the add-on zones. Each zone has a
width measured
along the tobacco rod 22 and a transverse cross-measure dimension in the
circumferential
sense of direction of the tobacco rod 22. For this embodiment, the zone width
is less than the
longitudinal pitch of the associated region. As seen in FIG. 2, the
longitudinal pitch length may
be greater than the corresponding zone width of the corresponding region. The
add-on zones
of successive regions along the tobacco rod 22 are preferably offset from the
add-on zones of
the adjacent regions, thereby defining a pattern 30 of regions which cover
portions of the base
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8
web along lines inclined relative to the edge of the base web. Furthermore,
the pattern of add-
on zones may repeat itself at least partially along the length of the base
web.
In the illustrated embodiment (FIG. 2), each zone is placed on the wrapper
paper 24 so
that the zone is centered upon one of three paths 34, 36, and 38, which paths
are represented
by corresponding broken lines 34, 36 and 38. Thus, for example, path 34 passes
through the
corresponding geometric features of six zones 34a, 34b, 34c, 34d, 34e, 34f.
Each zone is
spaced from the other zones, but the zones could, alternatively, contact one
another. The paths
34, 36 and 38 are parallel to each other and oriented at an acute angle 0
relative to the side
edge of the wrapper paper 24. It is to be realized that zones 36' are
preferably the same as
o
zones 36 and result from progression through the pattern shown in FIG. 2
where, as zones 34
disappear along one edge, zones 34' appear along the opposite edge. Each pair
of cross-web
aligned zones, e.g., zones 34a, 36a, or zones 34b, 36b, may cover up to about
33% of the total
surface area of the corresponding region 31a, 31b. For rectangular zones, each
zone is
preferably in the range of about 8nnm to about 10mm in the longitudinal
direction or width, and
about 5mm to about 7mm in the circumferential cross-measure direction.
Longitudinal spacing
33 between the zones preferably lies in the range of 4mm to about 12mm, and
more preferably
in the range of about 6 to about 8 mm. The circumferential spacing of the
zones of add-on
material is preferably in the range of about 3mm to about 20mm, more
preferably in the range of
about 5mm to about 8mm, and most preferably in the range of about 5.5mm to
about 7.0mm.
When wrapper paper 24 is formed about tobacco to make a tobacco rod 22, zones
of
add-on material at any longitudinal location are preferably spaced about 180
degrees from each
other. Moreover, the ratio of the area occupied by zones of add-on material to
the total area,
the total area being the sum of (i) the corresponding region 31d and (ii) the
annular area
between adjacent regions on one side (that ratio here being defined as the
"zone area ratio") is
substantially less than one. Preferably, that zone area ratio lies in the
range of less than about
20% to less than about 50%, and more preferably in the range of less than
about 20% to less
than about 35%. More particularly, in some embodiments the zone area ratio for
zone-occupied
area to total area may be less than 30%, and even less that 25%. Generally
speaking, it is
desirable to keep the zone area coverage ratio low because high values (i.e.,
closer to 1) are
believed to increase carbon monoxide concentration in mainstream smoke where
low
permeability (i.e., low Coresta) wrapper paper is used for the tobacco rod.
When the wrapper paper 24 is formed to make the tobacco rod 22, the paths 34,
36, 36'
describe a first helical path 36/36' (zones 36 and 36' in FIG. 2 combine to
form a helical path
36/36') and a second helical path 34 (comprising helically aligned zones 34)
both of which
extend lengthwise, around axis A, and over the length of the tobacco rod 22,
as illustrated in
FIGS. 7-9. The helical paths 36/36' and 34 (as seen from FIG. 2) have a helix
angle 0 and do
not intersect one another. Preferably, both helical paths may follow one of a
counterclockwise
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9
and clockwise rotation about the tobacco rod 22. As illustrated, both paths
34, 36' follow a
clockwise path, starting at the filter end of the tobacco rod 22, when viewed
from the lit end and
looking towards the filter end.
The zones of the pattern 30 may be formed by applying one or more layers of an
aqueous film-forming composition to the base web of the wrapper paper to
reduce the
permeability of the paper in those zones. Alternatively, a cellulosic material
may also be used to
form the zones. Where a film-forming composition is used, that film-forming
composition
preferably may include water and a high concentration of an occluding agent,
e.g., 20% to about
50% by weight. The film-forming compound can include one or more occluding
agents such as
starch, alginate, cellulose or gum and may also include calcium carbonate as a
filler. Where
starch is the film-forming compound, a concentration of about 24% may be
advantageous. The
film-forming composition may be applied to the ba'se web of the wrapper paper
24 using gravure
printing, digital printing, coating or spraying using a template, or any other
suitable technique.
For example, the film-forming compounds and methods for applying film-forming
compounds
described in publication number US 2007/102017,
may be chosen for applying a pattern to the base web of
the wrapper paper. If desired, the zones of add-on material can be formed by
printing multiple,
successive layers, e.g., two or more successive layers registered or aligned
with one another.
Furthermore, when layers are used to form the zones of add-on material, the
material in layers
may be the same of different. For example, one layer may be starch while the
next layer may
be starch and calcium carbonate (or vice versa).
The presently preferred embodiment for the pattern 30 of zones of add-on
material is
illustrated in FIG. 3. Like the embodiment of FIG. 2, the zones of add-on
material in FIG. 3 are
quadrilateral, specifically, generally rectangular. Preferably, at least two
zones, e.g., 40a, 40b,
of add-on material are applied in each region 31a, 31b, 31c, 31d so as to be
circumferentially
spaced in the finished smoking article. The circumferential dimension of each
zone 40a, 40b is
preferably selected to be less than about 50% of the cross-measure of the base
web 24 when
unwrapped, and most preferably about 25% of the cross-measure of that base web
24 or of the
circumference of the tobacco rod 22. The circumferential dimension of each
zone 40a, 40b,
when added to the circumferential spacing of between the zones 40a, 40b,
preferably is about
50% of the circumferential cross-measure of the base web 24.
The longitudinal length of the zones 40a, 40b plus the longitudinal spacing 33
between
the zones 40a, 40b, and zones 42a, 42b, (i.e., the longitudinal pitch length)
is preferably
selected so that three or four regions 31a, 31b, 31c, 31d will occur in the
nominal length of the
tobacco rod 22 of the smoking article and such that add-on zones of adjacent
regions are
spaced from one another longitudinally. Preferably, the longitudinal expanse
or "width" of the
zones, e.g., 40a, 40b (i.e., the zone width or region width as previously
defined) lies in the range
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of about 8mm to about 10mm. The circumferential offset, x, between (i) the
zones 42a, 42b of
the region 31b and (ii) the zones 40a, 40b of the region 31a preferably lies
in the range of about
10% to about 35% of the total, unwrapped cross-measure of the base web 24.
More preferably,
the circumferential offset, x, lies in the range of about 12% to about 35% of
the total, unwrapped
5 cross-measure of the base web 24. Most preferably, the circumferential
offset, x, is about half
the circumferential dimension or cross-measure of the add-on zone 40a, 40b.
The zones of
add-on material in other regions, 31c, 31d, are likewise further offset
circumferentially by the
same offset, x, with respect to each other. It will be noted that, for
example, in region 31d one
of the zones 46a, 46c of add-on material gets split between the two edge
portions of the base
io web 24 when the base web is in an unwrapped condition.
The pattern applied in regions 31a-31d preferably repeats along the length of
the base web 24.
Clearly, if the circumferential offset, x, is less than 12.5% of the cross-
directional width of the
base web, more than four regions will define a complete cycle or phase length
for the pattern
30. Conversely, if the circumferential offset, x, is greater than 12.5%, less
than four regions will
define a complete cycle length for the pattern 30 (as in the case of the FIG.
2 pattern).
A further embodiment of the pattern 30 (see FIG. 4) uses quadrilateral zones
60a, 60b of add-
on material, namely substantially parallelogram-shaped zones. While the zones
60a, 62a are
arranged so as to be in general helical alignment with one another when the
wrapper paper is
formed into a tobacco rod 22, the configuration of the parallelogram shapes
60, 62, 64, 66 may
be selected as desired. For example, the mirror images of the shapes (mirrored
about the
longitudinal direction) could be used, even though the general helical
impression might be lost.
Likewise, the skewness of the parallelogram zones may be changed as may be
desired.
Generally, however, the circumferential dimensions, circumferential spacing or
offset,
longitudinal dimensions, and longitudinal spacing or offset of the zones 60,
62, 64, 66 and the
regions 31a-31d in this embodiment may be selected as described in other
embodiments.
Still another embodiment of the pattern 30 (see FIG. 5) uses quadrilateral
zones 70, 72,
74, 76 of add-on material, namely substantially trapezoidal zones. Here again,
the generally
trapezoidal zones 70a, 72a may be arranged so as to be in general helical
alignment with one
another when the wrapper paper is combined into a tobacco rod 22. In addition,
the actual
shape of the trapezoidal zones 70, 72, 74, 76 may be selected as desired. For
example, the
skewness of the trapezoidal zones, and the proportions of the trapezoidal
zones may be
changed as may be desired. Generally, however, the circumferential dimensions,
circumferential spacing or offset, longitudinal dimensions, and longitudinal
spacing or offset of
the zones 70, 72, 74, 76 and the regions 31a-31d in this embodiment may be
selected as
described in other embodiments. It is preferred that the leading edge 7 be the
longer of the two
parallel edges of the zones 70.
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Yet another embodiment of the pattern 30 (see FIG.6) uses generally triangular
zones
80, 82, 84, 86 of add-on material. The generally triangular zones 80a, 80b of
region 31a may
be constructed and arranged so as to touch the corresponding generally
triangular zones 82a,
82b of the next adjacent region 31b. If the IP and SE characteristics desired
require it, the
generally triangular zones 80a, 80b of the first region 31a may be
longitudinally spaced from the
triangular zones 82a, 82b of the adjacent region 31b. Depending on the
characteristics required
for the smoking article design, it is also contemplated that the generally
triangular regions may
be oriented so that the burning coal of a smoldering smoking article
encounters the triangular
apex and gradually increasing cross-directional dimension of the generally
triangular zones (i.e.,
io from right-to-left in FIG. 6), or such that the burning coal of a
smoldering smoking article
encounters the base of the triangular zones and an abrupt increase in the
lower permeability
zones (i.e., from left-to-right in FIG 6). Circumferential spacing of the
triangular zones 80, 82,
84, 86 and the size of those triangular zones may be determined in accordance
with the
preferred ranges set out elsewhere in this description. Moreover, the
triangular zones may be
isosceles triangles as depicted, or equilateral triangles, or right triangles,
or any other desired
triangular shape that may be desired. Generally, however, the circumferential
dimensions,
circumferential spacing or offset, longitudinal dimensions, and longitudinal
spacing or offset of
the zones 80, 82, 84, 86 and the regions 31a-31d in this embodiment may be
selected as
described in other embodiments. Preferably, the triangular forms of the zones
80 are oriented
so that a leading edge 4 (closest to an approaching coal) is established.
Three different positions of the smoking article 20 resting on substrate 98
are illustrative
of the cooperation which occurs between the zones of low permeability add-on
material and the
substrate 98. One position (see FIG. 7) illustrates a side view of the smoking
article 20
according to this description. Rotation of the smoking article through a 45
degree angle about
its longitudinal axis (clockwise from the left end of FIG. 7) results in an
elevation similar to that
shown in FIG. 8. Similarly, further rotation of the smoking article 20 through
another 45 degree
angle (also clockwise from the left end of FIG. 7) results in an elevation to
that illustrated in
FIG. 9. In each of FIGs. 7-9 it can be seen that at least one pair of zones of
add-on material are
positioned on the sides of the smoking article at a location along the length
of the tobacco rod
22, e.g., zones 92, 92' of FIG 7, zones 94, 94' of FIG. 8, and zones 96, 96'
of FIG. 9. At those
locations where the zones of add-on material are positioned substantially on
the sides of the
smoking article 20 (FIG. 12), the zones 92, 92' are substantially upright or
generally
perpendicular to the surface of the substrate 98. That orientation of the
zones 92, 92' is best
illustrated in FIG. 12, where the opposed zones 92, 92' are located on
corresponding opposed
sides of the smoking article 20 when viewed in cross section, substantially
symmetrically
positioned relative to a diameter of the tobacco rod 22, which diameter is
substantially parallel to
the surface of the substrate 98.
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Orientation of the zones of add-on material at other longitudinal locations
along the
smoking article 20 are shown in FIGs. 10 and 11.
In FIG. 10, the zones 90, 90' of add-on
material are positioned such that one zone 90 touches the substrate 98. The
zones 94, 94' of
the smoking article 20 in FIG. 7 would also be positioned as in FIG. 10, when
viewed from the
right end of FIG. 7. In FIG. 11, one zone 96' contacts the substrate 98, but
the other opposed
zone 96 is located at the top of the smoking article 20. From consideration of
FIGs.7-9, it will be
appreciated that regardless of the angular position of a smoking article 20
having the pattern of
zones of add-on material described, at least one pair of opposed zones of add-
on material are
positioned as shown in FIG 10, or FIG. 12, or a rotated position between those
positions. This
io position has been referred to above as the oriented snuffer region 101.
When the smoking article 20 exists in free-burn condition (see FIG. 14), the
zones 92,
92' obstruct airflow to the burning coal of the tobacco rod 22 by virtue of
their reduced
permeability. On the other hand, the bottom portion 104 of the wrapper paper
freely permits air
to enter the side of the tobacco rod 22 to support combustion of the coal. A
vastly different
situation occurs when the smoking article 20 is placed on a substrate 98 (see
FIG. 13). Here,
the substrate 98 blocks the flow of air upwardly to the bottom portion 90 of
the tobacco rod 22.
The zones 92, 92' and the substrate 98 cooperate to define much smaller areas
100, 102
through which air can be delivered through the base web. More specifically,
the vertical area
100 between the bottom of the zone 92 and the substrate 98 and the vertical
area 102 between
the bottom of the zone 92' and the substrate 98 present a substantial
reduction in the area
through which air can pass to reach the smoldering coal of the tobacco rod 22.
As a result of
deprivation of oxygen in the air, the smoldering coal self-extinguishes when
the burn line
reaches opposed zones of add-on material positioned as depicted in FIG. 13.
The condition of
substantially reduced area for air to support burning of the coal also exists
for rotational
positions of the tobacco rod 22 between that position illustrated in FIG. 10
and the position
illustrated in FIG. 12 when the zones of add-on material do not contact the
substrate 98, with
FIG. 12 representing the position of most reduction in the area accessible to
airflow. Similarly, if
the smoking article is placed on a substrate 98 in a position where any of the
other pairs of
zones of add-on material have substantially the position shown in FIG. 13,
self-extinguishment
will also likely occur at such other pairs of zones.
However, when the smoking article is placed on the substrate 98 such that one
of the
add-on zones contacts the substrate 98, substantially as shown in FIG. 11, the
add-on zones
may sufficiently restrict the area through which air can pass to the base web,
and there is a
lesser degree of material cooperation between the substrate 98 and the add-on
zones to effect
a reduction in that area, in comparison to what occurs at the snuffer zone(s)
101.
In the foregoing example, the reduction in ignition propensity value,
reduction in self-
extinguishment value, and improved free-burn quality of a smoking article 20
having a wrapping
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13
paper with pattern 30 formed thereon is discussed in relation to a situation
where the smoking
article happens to be placed on a substrate 98 at one of three specific
orientations, the
orientations being spaced (off-set) 45 degrees apart from each other.
Naturally, the discussion
proceeded in this manner for the sake of brevity. It will be readily
understood that a pattern
according to this description can extinguish the smoking article, regardless
of which side portion
rests against a substrate 98 and without a need for applying film-forming
compound to the paper
to such an extent that a desirable free-burn quality in the smoking article is
lost. This may be
understood by recognizing that opposing zones of film-forming compound need
not appear at
locations exactly 90 degrees from the side portion in contact with the
substrate 98. Those
io zones may be centered at a location that is closer to or farther from
the side portion in contact
with the substrate 98, for example, between about 60 degrees and 120 degrees
from the side
portion in contact with the substrate 98.
Additionally, for a particular chosen pattern, the ability to extinguish the
smoking article
may depend more on providing minimum lengthwise extent of add-on material
(e.g., a film-
forming compound), rather than a particular weight per area of film-forming
compound at
longitudinal locations. The length of a rectangular zone, for example, may be
no less than
about 5.5mm for a particular design, base web, and film-forming compound used.
The amount
of film-forming compound used may be increased to improve ignition propensity
performance,
usually without losing a free-burn quality, and if desired, a burn accelerator
may be applied to
the paper to support even higher add-on levels.
Preferably, the zones of add-on material reduce permeability of the wrapper
paper to the
range of from about 0 to about 10 Coresta.
Previously, it was thought that a permeability ratio of 3:1 between the base
web and
zones of add-on material was insufficient to extinguish the smoking article
because there is an
insufficient reduction in the permeability of the paper at the longitudinal
location. However, that
permeability ratio, over a portion of the circumference of the smoking
article, can be sufficient to
extinguish the smoking article when the add-on material is located at sides of
the smoking
article not in contact with the substrate 98 and when there is an underlying
substrate 98.
Accordingly it is seen that the spirally rotated position of the opposed zones
of add-on
material creates a situation where, regardless of which side portion of the
wrapper paper is
placed against the substrate 98, there will always be at least one
longitudinal location having
film-forming compound at side portions not in contact with the substrate 98
yet having a
sufficient add-on amount and geometry that the zones can cooperate with the
substrate 98 to
self-extinguish the smoking article when the burn line reaches that
longitudinal location. This
fact results in improved ignition propensity performance of the smoking
article and permits a
smoking article to be designed with an ignition propensity value no greater
than 25%.
Nevertheless, in the absence of a substrate 98, the smoking article does not
self-extinguish yet
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14
maintains a free-burn, such as when the smoking article is held by a smoker.
This fact results in
improved self-extinguishment performance of the smoking article and permits a
smoking article
to be designed with an self-extinguishment value no greater than 50%, that
self-extinguishment
value may be the self-extinguishment average value, self-extinguishment values
at 0 degrees
may be much lower that the SE average value and may be less than 25%.
In the embodiments described above, the smoking article has a generally
circular cross
section. Therefore, it is possible for any side portion of the smoking article
to rest against the
substrate 98. However, a pattern as taught herein can be such that the burn
characteristics
described above (ignition propensity values no greater than 25% and E values
no greater than
50%) in relation to FIGS. 13 and 14 can be realized, regardless of which side
portion of the
smoking article happens to rest against the substrate 98. Preferably, the
pattern is selected so
that when the base web is wrapped around a tobacco rod 22, zones of film-
forming compound
appear at opposing sides not in contact with the substrate 98 at one or more
longitudinal
locations along the tobacco rod 22. Having more than one longitudinal location
with film-forming
compound at the side positions is preferred so as to accommodate situations
where the
smoking article is placed on a substrate 98 after the burn line has advanced
through a portion of
the smoking article which would have extinguished the smoking article, or so
that side zones of
add-on material are always relatively close to a burn line when the smoking
article is placed on
the substrate 98.
If desired, the zones of add-on material may also comprise other geometric
shapes other than
quadrilaterals including, for example, ovals, other polygons, or the like.
Further, the helix angle 0 described above may be increased while keeping the
dimensions of zones the same as in the illustrated embodiments. That change
can place the
zones in an overlapping pattern (or at least place zones in close proximity to
one another).
Alternatively, a stepped helical pattern may be formed by increasing the cross-
directional
dimension of the zones or patches while the helix angle is the same as in FIG.
2 and/or a zone
of equal size to that shown in FIG. 2 may be placed between each patch and
along paths 34,
36, 36' (so that there are 12, instead of 6 patches along a path 34).
When the word "about" or the word "approximately" is used herein in connection
with a
numerical value, the intent is to include not only that numerical value but
also values within in a
tolerance or range of 5% of the precise numerical value associated with the
corresponding
word "about" or the word "approximately".
It will now be apparent to those skilled in the art that this specification
describes a new, useful,
and nonobvious smoking article. It will also be apparent to those skilled in
the art that numerous
modifications, variations, substitutes, and equivalents exist for various
aspects of the smoking
article that have been described in the detailed description above.
Accordingly, it is expressly
CA 02684848 2014-11-06
intended that all such modifications, variations, substitutions,
be embraced thereby.
