Note: Descriptions are shown in the official language in which they were submitted.
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Improvements relating to Smoking Articles and filters therefor f
The present invention relates to an improved filter for smoking articles and
to smoking
articles incorporating such a filter. More particularly, it relates to a
filter for a cigarette.
For many years, cigarette manufacturers have attempted to reduce the amount of
smoke constituents delivered to a smoker by means of filtration. Much effort
has been made
to provide a smoking article that, when smoked, has a reduced bandwidth and a
puff profile
with reduced variance between puffs. The bandwidth of a smoking article is a
measurement
ratio between the tar delivery of a cigarette smoked under testing conditions
of the
International Standards Organization (ISO) versus the tar delivery of the same
cigarette
smoked in other, usually more intense conditions.
Specifically, ISO testing conditions involve the smoking of a cigarette
wherein the puff
volume is 35 mL, the puff duration is two seconds, and the interval between
puffs is 60
seconds. More intense smoking conditions may include an increase in puff
volume, an
increase in puff duration, a decrease in time between puffs, or some
combination of these
changes. A lower bandwidth corresponds to a decreased variance in the amount
of smoke
constituents delivered by a cigarette when smoked under ISO conditions and by
the same
cigarette smoked under more intense smoking conditions.
The puff profile of a cigarette is the delivery of smoke constituents per puff
recorded
against puff number. A puff profile having reduced variance between puffs,
i.e., a relatively
flat puff profile, is one in which the delivery of smoke constituents is more
consistent in each
puff during smoking.
Unfortunately, a flat puff profile does not usually result when conventional
cigarettes
are smoked. It has been known for some time in the tobacco industry that
delivery of smoke
particulate phase constituents, or "Total Particulate Matter" (TPM), is not
uniform during
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smoking. Under ISO machine smoking conditions, the "strength" per puff-
measured by the
amount of smoke particulate phase constituents in each puff-increases
significantly from the
first puff to the last. This increase in particulate matter in later puffs is
caused by a number of
factors, including a decrease in filtration efficiency of the tobacco rod, a
decreased level of
ventilation of the tobacco rod through the cigarette paper-both of which
result from the
length of the tobacco rod being reduced during smoking-and an increased smoke
particulate
phase constituent potential of the tobacco rod due to the deposition of smoke
particulate phase
constituents from the earlier puffs onto the rod.
The ratio of smoke constituents between the first to last puffs in a cigarette
varies
based on a number of product design characteristics, including the total smoke
constituent
yield for that product. Typically, ratios of between 2 and 4 for "full flavor"
products (having
more than10 mg TPM), between 3 and 5 for "lights" (5-10mg TPM), and between 4
and 6 for
"ultra lights" (less than 5mg TPM) are achieved under ISO machine smoking
conditions. The
higher levels of ventilation used in the "light" and "ultra light" products
cause the ratio to
increase even as the products' smoke constituent yields decrease. This
imbalance in the yield
of smoke constituents between the first and last puffs in a cigarette can lead
to consumer
rejection of the product due to a perception that the cigarette is too "weak"
in the first few
puffs or too "strong" in the final few puffs. This problem is exacerbated for
the products
yielding a lower level of smoke constituents due to the much larger
differences between the
amount of smoke constituents in the first and last puffs. Accordingly, there
is a desire to
provide a cigarette with a flatter puff profile that is able to deliver a
similar level of smoke
constituents in both the first and last puffs.
Furthermore, it is known that the increased level of smoke constituents
delivered in the
final few puffs represents a significant proportion of the total amount of
smoke constituents
generated in all cigarette products. Consequently, by reducing the delivery of
smoke
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constituents in the final few puffs, the amount of smoke constituents
delivered in total will
also be reduced.
Accordingly, it is an object of the present invention to provide a smoking
article filter
which efficiently and effectively reduces the delivery of smoke constituents
delivered to a
consumer in use.
It is a further object of the present invention to provide a smoking article
filter which is
capable of decreasing the bandwidth of a smoking article andlor which is
capable of
decreasing the variance of smoke constituent delivery between puffs.
The invention comprises a filter for smoking articles having at least two
different
sections. A first section comprises an inner area and a surrounding area, the
inner area and the
surrounding area comprising a smoke flow path and an area of relatively smoke
impervious
material. The relatively smoke impervious material has increased flow
resistance when
compared to the smoke flow resistance of the smoke flow path. In one
embodiment, the
smoke flow path and the relatively smoke impervious material are arranged in a
core and
annulus configuration, with the smoke flow path forming the core. In an
alternative
embodiment the smoke flow path forms the annulus and the relatively smoke
impervious
material forms the core of the first section.
The second section comprises a smoke impaction zone in axial alignment with
the
smoke flow path of the first section. The second section of the filter may
comprise a core
comprising high pressure drop filter material and an annulus comprising a
lower pressure drop
material than the core or vice versa.
In one embodiment of the filter of the present invention, the first and second
sections
are spaced apart from one another by means of an intervening gap.
In one embodiment of the invention, the filter is designed such that the smoke
flow
path of the first section is axially aligned with the core of the second
section. In this
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embodiment, the core of the second section is made of high pressure drop
filter material when
compared to the filter material of the annulus of the second section. In use,
smoke exits the
smoke flow path of the first section such that a large portion of the smoke-
especially the
heavier smoke constituents-impact on the high pressure drop core of the second
section.
Alternatively in this embodiment, a plug of relatively smoke impervious
material may be
located in the second section in axial alignment with the exit of the smoke
flow path of the
first section such that a large portion of the smoke-especially the heavier
smoke
constituents-impact on the plug of relatively smoke impervious material on the
second
section. Impaction filtration occurs when smoke particles hit a material and
are retained by it,
thus in the embodiments described above, smoke components impacting on the
smoke
impaction zone of the second section will be retained thereby.
In another embodiment, the invention further comprises ventilation holes
circumscribing the second section or circumscribing the space or gap between
the first and
second section. When the cigarette is smoked, the smoke flow path of the first
section begins
to fill with particulate smoke constituents that condense and are deposited in
the smoke flow
path, and the smoke flow through it begins to become restricted. This
restriction leads to an
increase in the pressure drop in the first section. As the pressure drop
increases, more air is
brought into the filter through the ventilation holes, thereby, as smoking
proceeds in
subsequent puffs, causing a decrease in the variance in the delivery of smoke
constituents in
subsequent puffs that would otherwise occur as smoking proceeds due to the
known
phenomenon of increasing smoke constituent delivery in the later puffs of a
smoking article.
Ventilation may be provided by means known to the skilled artisan, such as
laser or
mechanical perforation.
The filter may further comprise additional sections. The additional filter
sections may
comprise conventional filtration material such as, for example, cellulose
acetate,
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polypropylene or paper. The additional filter sections may altematively or
additionally
comprise carbonaceous material for example, activated charcoal, resin material
for example,
amberlite, duolite or the like, and/or catalytic material.
The present invention further provides a smoking article comprising a rod of
smokable
material, a wrapper circumscribing the rod of smokable material, and a filter
according to the
present invention attached to the rod of smokable material.
The first section of the filter according to the invention is preferably
adjacent to the rod
of smokable material of the smoking article at a first end and is spaced from
the second section
of the filter at an opposed end.
The filter of the present invention and the rod of smokable material may be
interattached by any means known in the art such as, for example, a tipping
wrapper. As is
commonly known, the tipping wrapper may circumscribe the filter along its
length and overlap
with the rod of smokable material. The tipping wrapper may be attached to the
wrapper of the
rod of smokable material by conventional means, for example, by adhesive.
In the smoking article of the invention, the filter and the rod of smokable
material are
preferably in co-axial alignment with one another.
In one embodiment of the smoking article according to the invention, the
filter may
comprise one or more additional filter segments. The additional filter
segment(s) may be
located between the rod of smokable material and the first filter section,
and/or may be located
at the mouth end of the second filter section.
The aspects and advantages of the present invention will be better understood
when the
detailed description of the preferred embodiment is taken in conjunction with
the
accompanying drawings, in which:
Fig. 1 is a perspective view of a cigarette with selected portions shown in
cut-away;
and
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Fig. 2 is a cross-section of an embodiment of the cigarette shown in Fig. 1;
Fig. 3 is a cross-section of another embodiment of the cigarette shown in Fig.
1;
Fig. 4 is a perspective view of another embodiment of the cigarette shown in
Fig.l;
Fig. 5 is a perspective view of yet another embodiment of the cigarette shown
in Fig. 1;
Fig. 6 is a graphical representation of the effectiveness of several
embodiments of the.
invention in reducing total particulate matter, and
Fig. 7 is a graphical representation of the effectiveness of one embodiment of
the
invention in reducing bandwidth.
While this invention is capable of embodiments in many different forms,
multiple
embodiments are shown in the figures and will be herein described in detail.
The present
disclosure is to be considered an exemplification of the principles of the
invention and is not
intended to limit the broad aspects of the invention to the embodiments
illustrated.
Referring now to Figure 1, the invention comprises a cigarette filter 1 and a
cigarette 3
designed to reduce the delivery bandwidth of a cigarette in use. The cigarette
3 comprises a
tobacco section 18 and a filter 1. The filter 1 comprises a first section 2
comprising an inner
area 4 and a first surrounding area 6. In one embodiment, the first section 2
is on the end of
the cigarette 3 nearest to the tobacco section 18. The diameter of the inner
area 4 is
preferably between 0.5 and 3.0 mm and between 5 and 10 mm in length. It will
be understood
that the length of the smoke flow path will be determined by the length of the
filter; the length
of the smoke flow path of the first section, however, will be equal to the
length of the first
section.
For the filter to function properly, the inner area 4 and the surrounding area
6 should
comprise a smoke flow path and an area that is relatively impervious to smoke.
In the
preferred embodiment, the inner area 4 is the smoke flow path and the
surrounding area 6 is
impervious to smoke. In this embodiment, the smoke travels through the smoke
flow path 4
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and exits the cigarette at a high velocity. In another embodiment, however,
the smoke flow
path can be formed by the surrounding area 6 with the inner area 4 being
formed of smoke
impervious material.
The smoke flow path 4 can take on a number of different embodiments. For
example,
the smoke flow path 4 can comprise a tube 30, as shown in Fig. 2, or a lower
pressure drop
materia140-such as cellulose acetate-than that of the surrounding area 6, as
shown in Fig.
3.
Referring again to Fig. 1, the filter 1 further comprises an axially aligned
second
section 8 comprising a core 10 circumscribed by an annulus 12. The inner core
10 of the
second section 8 is axially aligned with the inner area 4 of the first section
2. As can be more
clearly seen in Figure 2, the filter I further comprises a space or gap 14
situated between the
first section 2 and the second section 8. The gap 14 can be in the range of
0.0001 mm to 4 mm
in length, but in various embodiments of the invention may be in the range of
0.1 - 3.8 mm,
or in the range of 0.5 - 3.5 mm, or in the range of 1- 3 mm, or in the range
of 1.5 - 2.5 mm,
and in one particular embodiment of the invention is about 2 mm. If the gap is
too wide, the
heavier smoke constitaents will diffuse within the gap 14 between the first
and second filter
sections before impacting the second section 8, which would negatively impact
the
performance of the filter 1. Along with the rest of the filter 1, the gap 14
is wrapped in plug
wrap and attached to the rest of the cigarette with conventional tipping
paper.
Either the core 10 or the annulus 12 of the second section 8 must form an
impaction
zone of relatively smoke impervious material. If the smoke flow path in the
first section is the
inner area 4, then the impaction zone of the second section 8 will be in the
region of the core
10. The smoke impaction section can extend along the whole length of the
second section 8,
as shown in Figs. 1-3, or as shown in Figure 4, it can be a small disc 32 of
smoke impervious
material attached to the end of a regular filter section 34. In the embodiment
shown in Figure
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4, smoke would diffuse behind the smoke impervious material, but the heavier
smoke
constituents would first be removed by their impaction on the small disc 32.
If the smoke flow path in the first section 2 is the surrounding area 6, then
the
impaction zone of the second section 8 will be in the region of the annulus
12. As shown in
Figs. 1-3, this can be an annulus 12 of relatively impervious material along
the whole length of
the second section 8, or it could be an annular disc 36 of the same material
affixed to the end
of the regular filter section 34, as shown in Fig. 5.
When the core 10 acts as the impaction zone, the diameter of the outer annulus
12 is
preferably 40% of the total diameter of the filter 1, but the filter will
function properly,
however, as long as the core 10 is wider than the exit diameter of the smoke
flow path of the
first section 2. Likewise, when the annulus 12 acts as the impaction zone, its
width should be
bigger than that of the smoke flow path formed by the surrounding area 6.
The length of the second section 8 can be any length to make up the desired
total
length of the filter 1, and it is usually about 5 to 50 mm. The second section
8 is generally the
mouth end of the cigarette filter.
In one embodiment, the filter 1 further comprises ventilation holes 20, which
can be
positioned in either the second section 8 or the gap 14.
The filter 1 reduces the delivery bandwidth in two different ways. Firstly,
when the
cigarette is being smoked, the smoke passes through the smoke flow path of the
first section 2
and enters the gap 14 at high velocity. Due to the short distance between the
filter sections 2,
8 and the high velocity at which the smoke travels, most of the smoke
particles do not disperse
before impacting and sticking on the high pressure drop material of the second
section 8
opposite the smoke flow path of the first section 2. The heavier smoke
particles disperse less
than the lighter particles, which leads to less total particulate matter
leaving the cigarette. The
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harder the puff on the cigarette, the less dispersion of the smoke occurs, and
the more filtering
that takes place.
The second way that bandwidth is reduced involves the use of ventilation
holes. As
the cigarette is smoked, the tube 4 in the first section 2 progressively fills
with particulate
smoke constituents, which increases the resistance to smoke flowing through
the tube 4. This
increases the pressure drop through the first section 2, which causes more
diluting air to be
pulled through the ventilation holes 20 when the smoker inhales. The diluting
air enters the
gap 14 or the second section 8 through ventilation holes 20 circumscribing the
second section
8 or the gap 14. This further concentrates the smoke in the middle of the gap
14, thereby
causing most of the smoke to impact the core 10, which in the preferred
embodiment
comprises the impaction area of the second section 8.
While there have been described what are believed to be the preferred
embodiments of
the present invention, those skilled in the art will recognize that other and
further changes and
modifications may be made thereto without departing from the spirit of the
invention, and it is
intended to claim all such changes and modificatioris as fall within the true
scope of the
invention.
EXAMPLES
Four different embodiments of the invention were tested to determine the
amount of
nicotine-free total particulate matter in each puff and to determine whether
the delivery
changed as the number of puffs increased. In Examples A and B, the first and
second sections
were 11 and 14 mm in length, respectively, and there was a 2 mm gap between
the sections.
In Examples C and D, the first section was 11 mm long and the second section
was 16 mm
long, and the gap between the two sections was 0.001 mm. All of Examples A, B,
C, and D
had a tube in the first section with an internal diameter of 2 mm. In Examples
A and C, the
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annulus of the second section was made of high pressure drop material, whereas
in Examples
B and D, the annulus of the second section was made of lower pressure drop
material.
Table I below and Fig. 6 demonstrate the beneficial effect that the invention
has on
smoothing out the puff profile when compared with a "control" cigarette:
TABLE I- Puff by Puff Delivety of Nicotine-Free Wet Particulate Matter (in mg)
Puff No. Control A B C D
1 1.068 mg 0.463067 0.443533 0.481333 0.129867
mg mg mg mg
2 1.29256 mg 0.652667 0.454827 0.519467 0.200733
mg mg mg mg
3 1.530667 mg 0.726933 0.625867 0.6452 mg 0.250267
mg mg mg
4 1.742667 mg 0.86 mg 0.7856 mg 0.6844 mg 0.216267
mg
5 2.012133 mg 0.904933 0.922667 0.737867 0.4012 mg
mg mg mg
6 2.320267 mg 1.098267 1.076907 0.767333 0.340933
mg mg m mg
7 4.366667 mg 1.272 mg 1.1432 mg 0.9592 mg 0.543333
mg
8 1.402667 1.462667 1.117333 0.737467
mg mg mg mg
Furthermore, Table 2 and Fig. 7 show the reduction in bandwidth that occurs
when one
embodiment of the invention-Example D-is smoked under various conditions. The
more
extreme the conditions, the better Example D performs compared to the control
cigarette. At
ISO conditions (puff volume of 35 mL, puff duration of 2 seconds, puff
interval of 60
seconds), the difference between the amounts of particulate matter is
relatively small. But as
the overall intensity of the puffs increases, the effectiveness of the filter
of the invention
improves, as is demonstrated by the large difference in TPM between the
control and Example
D.
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TABLE 2- Delivery of TPM at ISO and Other Conditions
Smoking Conditions Control D
ISO 4.95 mg 4.43 mg
60/2/60 9.16 mg 7.57 mg
45/2/30 11.5 mg 9.93 mg
60/2/30 15.54 mg 11.11 mg
The various embodiments of the invention have a measurable beneficial effect
on
decreasing the bandwidth, decreasing the TPM, and smoothing out the puff
profile of a
cigarette as it is smoked. It is apparent that the location of the high
pressure drop material and
the width of the gap will modify the performance of the invention while still
using concepts of
the present invention. Such variations are deemed to fall within the bounds of
the present
application.
