Note: Descriptions are shown in the official language in which they were submitted.
2021199
CIGARETTES
This invention relates to cigarettes which are of
improved uniformity as to the strength of the smoke, flavour
and aroma throughout the smoking.
It is well known that a conventional cigar or cigarette
filled with a tobacco of uniform quality grows stronger to
the taste and increases in nicotine delivery as it is
consumed as a result of the partial condensation, on the
unburnt tobacco, of nicotine and other smoke constituents
generated in early puffs and the subsequent release of these
materials along with the combustion products of the tobacco
in later puffs.
It has been proposed that the typical puff-by-puff
strength and flavour profile may be modified and made more
uniform by the use of tobaccos of different quality within
separate zones of the tobacco rod.
O.A. Elias (G.B. 8,577) proposed the use of discrete
segments with a different tobacco in each segment.
N.M. Hopkins (G.B. 250,063) disclosed the use of a
blend of strong tobacco which occupies a space of gradually
decreasing cross-section from the kindled end towards the
end through which the smoke is drawn with a tobacco of mild
composition filling the remainder of the space; for example,
the strong tobacco may be in the form of a cone.
G.B. 1,340,100 of B.A.T. suggests the use of natural
tobacco in a first smoked portion and reconstituted tobacco
or tobacco substitute in a second portion, the two portions
being in the form of two wedges or, alternatively, the first
portion being a core of conical or frusto-conical shape.
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G.B. 1,343,402 of Olin Corporation makes use of a
shredded carbon filled paper incorporated to replace tobacco
in increasing amounts towards the butt end of the cigarette
to achieve a more uniform yield of smoke as the cigarette is
consumed.
U.S. 4,759,380 of R.J. Reynolds Tobacco Company
described a cigarette in which the tobacco rod is composed
of two segments, each containing a different tobacco, with a
filter attached to the second segment; the second segment
may contain reconstituted tobacco, expanded tobacco,
processed tobacco stems or a blend thereof.
This concept of tobacco rods which vary in tobacco
composition along the length may be used to achieve a more
uniform puff-by-puff delivery of smoke but very often the
final one or two puffs are still found to be somewhat
stronger than the previous puffs as a result of the repeated
previous exposure to smoke of the tobacco being consumed in
the final stages.
In an alternative approach to achieve a more uniform
puff-by-puff profile, cigarettes with conventional tobacco
rods filled with a tobacco of uniform quality have been
provided with special filters which increase in filtration
efficiency during smoking.
Examples of such fllters are described in G.B.
2,102,271 A, G.B. 2,103,065 A, G.B. 2,105,566 A and G.B.
2,119,225 A of Filtrona (U.K.). These employ two flow
paths, a low pressure drop path of low filtration efficiency
and a high pressure drop flow path of high filtration
efficiency. During the early puffs, the smoke tends to flow
through the low pressure drop path, but a blocking mechanism
acting through the deposition of tar causes the flow of
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smoke to switch to the high pressure drop path in subsequent
puffs.
Other examples are described in U.S. 4,460,000 and U.S.
4,469,112 of Browne et al., and European Patent Application
No. 88308323.0 (publication No. 0 310 257) and European
Patent Applications Nos. 89310421.6 (Publication No. 0 364
253) and 89310430.7 (Publication No. 0 364 256) of Rothmans
International Tobacco (UK) Limited. These filters achieve
an increase in filtration efficiency, for example, by the
deposition of tar on fibrous filtration media when the flow
of smoke is confined to a narrow stream by passage through
orifices in impermeable o~ low permeability discs or tubes
contained within the filter.
G.B. Patent Application No. CA/90/00070 of Rothmans,
Benson and Hedges, Inc. and Rothmans International Services
Limited makes use of a fabric of microfine fibres to achieve
a variable filter efficiency. The fabric, which has a high
filtration efficiency but a low pressure drop, forms the
wrap of a core of low pressure drop, low filtration
efficiency tow which is enclosed by an annulus of higher
pressure drop, higher filtration efficiency tow. The core
is crimp-sealed at the end adjacent to the tobacco so that
smoke is able to flow either along the outer annulus or
through the cylindrical fabric wrap into the core~ The
deposition of "tar" on the microfine fibres produces
progressive increase in filtration efficiency during
smoking. An additional feature of this filter design is
that high filtration efflciencies can be achieved, even in
the early puffs, at a relatively low filter pressure drop.
All of these special features increase in pressure drop
during smoking and, if tip ventilated downstream of the
region of the increase in pressure drop, there arises a
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puff-by-puff increase in the level of tip ventilation which
assists in creating a more uniform delivery of smoke as the
cigarette is consumed.
These special filters are particularly effective in
minimising the increase in the smoke yields of the final two
puffs of the cigarette.
According to the present invention a cigarette or cigar
comprises a rod of tobacco which decreases in strength from
the kindled end to the other end and which is provided with
a filter, the filtration eEficiency of which increases as
the cigarette is consumed.
Preferably the tobacco rod comprises two or more
different types or blends of tobacco separated into
demarcated zones, the tobacco at the kindled end of the
cigarette being higher in strength and/or quality and/or
flavour and/or nicotine content than at the other end
through which the smoke is drawn.
The demarcated zones may be in the form of segments or
the zone of stronger tobacco can be wedge shaped, conical or
frusto conical.
Where there are wedges, cones or frusto cones of
stronger tobacco they may extend throughout substantially
the whole length of the tobacco rod.
Where the wedge conical or frusto-conical shape is used
over part of the length of the rod the kindled end may be
wholly of stronger tobacco.
The material forming the blend of strong tobaccos may
include cured and aged flue-cured, Burley, Maryland or
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Oriental tobaccos, or rare speciality tobaccos such as
Latikia or fire-cured tobaccos.
The material forming the blend of strong tobaccos may
also include expanded tobacco or minor amounts of
reconstituted tobacco sheet, processed stems or tobacco
substitutes.
The milder blend of tobaccos can include flue-cured,
Burley, Maryland or Oriental tobaccos or rare speciality
tobaccos of the milder varieties and these milder tobaccos
may also include expanded tobaccos, reconstituted tobaccos,
processed stems or tobacco substitutes.
Preferably the expanded tobaccos, reconstituted
tobaccos, processed stems or tobacco substitute can form of
majority part of the milder blend.
The filter may be of the kind set forth in European
Patent Application 88308323.0 (Publication No. 0 310 257),
the disclosure of which is incorporated herein. This filter
comprises a filter element of fibrous material, the fibres
of which extend longitudinally between a first end which is
for attachment to the tobacco rod and a second end, and
which surrounds a longitudinally extending tube member, one
end of which is closed and is located at the first end of
the filter element and the open end of which extends to the
second end of the element, the wall of the tube being
provided with one or more radially extending apertures
adjacent to its c]osed end to promote radial flow through
the fibres of the filter element adjacent the aperture or
apertures and being dimensioned so that they remain open to
allow flow communication through the wall of the tube
throughout the period that the cigarette is smoked.
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This type of filter is equally effective if assembled
to the tobacco rod in the reverse configuration with the
open end of the tube in abutment with the tobacco.
The interior of the tube may be empty or filled with a
column of filter material and in a preferred construction
the tube is formed by an impervious film.
In an alternative construction the filter may be of the
kind set forth in European Patent Application No. 89310430.7
(Publication No. 0 364 256) the disclosures of which are
incorporated herein and in which the filter comprises a
filter element having a~flow path therethrough which
includes a barrier in the form of a substantially planar
disc made from a layer of micro-fine fibres with a diameter
of between 0.5 and 10 microns, and provided with one or more
flow openings in the range of 0.1 mm to 3.0 mm in diameter
with a combined total area of between 0.1 mm2 and 10 mm2.
With this arrangement the disc can be located between
layers of porous material to form a laminate barrier.
In another alternative construction the filter may
comprise a filter element of the kind set forth in European
Patent Application No. 89310421.6 (Publication No. 0 364
253), the disclosure of which is incorporated herein and in
which the filter comprises a filter element which includes
an axially extending barrier tube of micro-fine fibres with
a diameter of between 0.5 and 10 microns and located so that
at least part of the gas flow passes through the wall of the
barrier.
The barrier tube can be provided with one or more flow
openings in the range of 0.1 mm to 3.0 mm in diameter with
a combined total area of between 0.1 mm2 and 10 mm2.
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Preferably the barrier tube is shaped to provide inner
and outer coaxial passages through the filter eiement, one
of which is closed at one end and the other of which is
closed at the other end so that the flow path passes through
the wall of the barrier tube.
With this arrangement the interior of the barrier tube
can be empty or it can be filled with a column of filter
material.
The filter may also be of the kind set forth in PCT
Patent Application CA/90/00070, the disclosure of which is
again incorporated in the present Application and in which
the filter comprises an annulus of conventional filter
material surrounding a cylinder of micro-fine fibres, a
smoke flow directing element insuring that all the smoke
drawn from the cigarette enters the annulus of conventional
filter material and a low resistance filtered smoke path is
provided at the interior of the cylinder of the micro-fine
fibres.
The invention can be performed in various ways and some
embodiments will now be described by way of example and with
reference to the accompanying drawings in which :
Figure 1 is a cross-sectional side elevation of a
~ cigarette incorporating the invention in which the
filter is of the kind described in European Patent
Application 88308323.0 (Publication No. 0 310 257);
Figure 2 is a cross-section of an alternative
construction with the same type of filter;
Figure 3 is another construction with the same type of
filter;
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Figure 4 shows another construction using the same type
of filter with an alternative tobacco arrangement;
Figure 5 shows another alternative tobacco arrangement;
Figure 6 shows the filter construction in more detail; ..
Figure 7 shows a cigarette with a tobacco arrangement
similar to that shown in Figure 5 but with an
alternative filter construction in which the tube is
filled with a plug of filter tow;
Figure 8 shows the filter construction in more detail;
Figure 9 shows a cigarette with a tobacco arrangement
similar to that shown in Figures 5 and 7 but with
another alternative filter construction of the kind set
forth in European Patent Application No. 89310430.7
(Publication No. 0 364 256);
Figure 10 shows a filter construction in more detail;
Figure 11 shows another cigarett.e construction
according to the invention with another alternative
filter construction of the kind set forth in European
Patent Application No. 89310421.6 (Publication No. 0
364 253); and,
Figure 12 shows a filter construction in more detail.
A cigarette according to the invention can utilise a
tobacco rod of circular or elliptical cross-section wrapped
with a suitable cigarette paper and filled with at least two
different types of tobaccos or at least two different blends
of tobacco separated into demarcation zones within the rod
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so that the tobacco in the region of the kindled end of the
cigarette is higher in strength and/or quality and/or
flavour and/or nicotine content than the tobacco in the
region through which the smoke is drawn.
In the arrangement shown in Figure 1 the demarcated
zones of tobacco are in the form of segments, the kindled
end of the cigarette being indicated by reference numeral 1
and containing a stronger tobacco than the other end of the
tobacco rod 2 through which the smoke is drawn. In none of
the drawings is the cigarette paper shown.
The filter indicated by reference numeral 3 is of the
kind described in European Patent Application 88308323.0
(Publication No. 0 310 257). It will be appreciated that
any of the filters described in this Patent Specification
can be used because they provide the necessary progressive
filtering effect. In the filter shown the filter rod
comprises a plug wrap 6, fibrous material 4 and a tube 5
placed longitudinally along the length of the filter. One
end of the tube 5 is closed by being crimped as indicated by
reference numeral 8 and the other open end of the tube is
indicated by reference numeral 9. A pair of opposed
apertures 7 are provided in the wall of the tube adjacent
the closed end 8. The construction of this type of filter
is more clearly shown in Figure 6.
The various dimensions of the tube are as shown in
Figure 2 of the European Patent Application referred to and
any of the other variations, as mentioned above, can be
employed.
When a cigarette fitted with this filter is smoked, the
smoke enters the filter rod and travels inside the fibrous
filter material until it reaches the location of the
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apertures in the tube. The smoke now splits into two
streams, one stream continues to flow inside the fibrous
filter material and the other stream flows into the tube
through the apertures. As the smoke stream which is
diverted into the tube has only been flowing through a short
length of the fibrous material the smoke has therefore not
been filtered as extensively as the other smoke stream. The
"tar" concentration of the smoke stream flowing out from the
tube in the first puff is therefore higher than that flowing
out from the main filter body. As the stream of smoke is
being diverted into the tube through the aperture, the flow
direction of the smoke is changed from being parallel to the
fibres to being at an angle. The radial component of the
flow has therefore greatly increased. In such flow
conditions, the fibres in the flow path of this smoke are
therefore transverse to the direction of flow. Furthermore,
both the velocity and momentum of the smoke particles are
greatly increased as they converge to flow through the
narrow apertures. The combined effects of the increased
radial component of the flow and the increased particle
momentum have consequently greatly increased the filtration
efficiency of the fibres in the vicinity of the apertures.
The smoke particles will deposit and accumulate partially on
the aperture and partially on the fibrous material around
the aperture. It has been found that the size of the
aperture and its location on the tube wall can be chosen so
that the aperture or apertures will not be completely
blocked by the accumulated smoke particles. Furthermore,
the size of the apertures and their location can be so
chosen that the accumulation of the smoke particles on the
fibres around the aperture will lead to an increase in the
filtration efficiency of these fibres to an extent related
to the quantity of smoke which is passed through the
aperture. The smoke stream inside the stream is tnerefore
being filtered less efficiently at the initial smoking
2021~ 9~
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period, where it is being filtered more and more efficiently
due to this gradual increase in the filtration efficiency as
the smoke process proceeds. The "tar" concentration of the
last few puffs is therefore very much reduced. Consequently
a cigarette fitted with this filter has a much more even
satisfying "tar" delivery and it is therefore possible to
arrange the dimensions of the filter to co-operate with the
construction of the two part cigarette rod so that a
substantially uniform strength of smoke flavour and aroma
are provided.
The combination of this type of filter and the two part
tobacco construction of the filter rod has thus enabled this
to be achieved, the particular effect of the filter
complementing the two part rod.
Figure 2 shows a cigarette rod construction in which
the zone of stronger tobacco 1 is wedge shaped and in Figure
3 the zone of stronger tobacco is conical. Figure 4 shows a
construction in which the zone of stronger tobacco is
frusto-conical. In all these constructions the milder
tobacco 2 fills the remainder of the space in the rod.
These wedges, cones or frusto-cones of stronger tobacco are
shown as extending throughout the whole length of the rod
but, if desired they may only extend for a portion of the
length.
In the construction shown in Figures 5, 6 and 7 the
strong tobacco 1 occupies the whole of the tobacco rod
cross-section for the first few millimetres of length from
the kindled end 10. Such tobacco rods may be produced by
the manufacturing process disclosed in European Patent
Application No. 0 307 090 of Rothmans, Benson and Hedges
Inc. and Rothmans International Services Limited. Other
suitable configurations are also disclosed in this European
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Patent Application.
The material forming the blend of strong tobacco may
include cured and aged flue-cured, Burley, Maryland or
Oriental tobaccos or rare speciality tobaccos such as
Latakia or fire-cured tobaccos. If desired, expanded
tobacco or minor amounts or reconstituted tobacco sheet,
processed stems or tobacco substitutes may be incorporated.
The material forming the milder blend of tobaccos may
also include flue-cured, Burley, Maryland or Oriental
tobaccos or rare speciality tobaccos but, in general, it is
advantageous when at least a proportion of these are milder
varieties. Other materials used in this milder blend may
include expanded tobaccos, reconstituted tobaccos, processed
stems or tobacco substitutes and these materials may form a
major portion of the blend.
As mentioned above the filter which is attached to the
end of the tobacco rod containing the higher proportion of
milder tobaccos and which has the special property of
increasing in filtration efficiency puff-by-puff during the
smoking of the cigarette can be as described in European
Patent Application 88308323.0 (Publication No. 0 310 257)
and the filter shown in Figure 7 is of another type also
described in that Patent Application. In this construction
the tube 5 as shown in Figures 1 to 6 is replaced by an
impervious film tube 12. As in the case of tube 5, tube 12
contains aperture 7, closed end 14 and open end 15.
Aperture 7 is in flow communication between fibrous material
13 and fibrous material 11. Preferably, the fibrous
material 11 is less densely packed than the fibrous material
13. Furthermore, the fibre diameter should be as large as
feasible. For example, a commonly available cellulose
acetate tow of between 5 to 15 denier per filament (dpf),
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lO,OOO to 50,000 total denier (T.D.) will be suitable.
Material 13 should be a filtration material of high
filtration efficiency. Preferably, material 13 will be the
commonly used cellulose acetate tow such as the tow of about
1.5 dpf to 5 dpf and preferably 1.5 dpf to 3.5 dpf.
When a cigarette fitted with this filter is smoked, the
smoke enters the filter rod where the closed end 14 is
located. The smoke initially flows through material 13.
When it reaches the vicinity of aperture 7, the smoke splits
into two streams; one stream of smoke continues to flow
through material 13; the other stream flows through the
aperture 7 and into materiaL ll. Both streams flow out of
the filter rod at the filter end where the open end 15 is
located. The embodiment has an additional advantage to that
shown in Figures l to 6. The main advantage is that
material ll in the vicinity of aperture 7 provides an
additional means for the smoke particle to be captured by
the mechanism of impaction as the smoke flows from aperture
7 into material 11. In fact, material ll not only provides
a filtration medium inside tube 12, it also provides an
impacting surface for the smoke particlas in the vicinity of
aperture 7. It is well known that the velocity and momentum
of the smoke particles will greatly increase when they flow
through a narrow and restricted passage such as aperture 7.
These conditions favour the capture of smoke particles by
impaction on the fibres of material ll which are transverse
to the flow direction of the smoke in the vicinity of
aperture 7. The captured smoke particles will gradually
build up inside material ll in the vicinity of aperture 7.
This build-up will further improve the capture efficiency as
the void volume there is reduced to a certain extent. The
function of material ll in the vicinity of aperture 7 has
clearly enhanced the overall aim of a gradual increase in
efficiency of the whole cigarette filter. Due to the novel
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idea of choosing the material 11 as a fibrous material of
low packing density, ie of large void volume, and/or fibres
of large diameter, the build-up of captured smoke particles
will never be sufficient to clog up the flow passage between
aperture 7 and open end 15 during the smoking period. The
danger of greatly increased flow resistance in such flow
passage is therefore avoided.
These types of filter as described in European Patent
Application No. 88308323.0 (Publication No. 0 310 257) are
especially effective if assembled to the tobacco rod in the
reverse configuration with the open end of the tube in
abutment with the tobacco.
In the construction shown in Figure 9 the filter is of
the kind set forth in European Patent Application No.
89310430.7 (Publication No. 0 364 256). In this
construction a filter rod is formed from an element which
comprises a tube 24, a barrier disc 23 provided with an
aperture 22 and made from a layer of micro-fine fibres
between 0.5 to 10 microns diameter. The tube 24 may be of
any convenient material such as paper or plastics material.
The edge of disc 23 is in close contact with the inside wall
of the tube 24 so that end-to-end flow path communication
through the tube has to pass through disc 23. The aperture
22 can be a single aperture or up to ten apertures, between
one and three apertures being preferred. A single aperture
may be located conveniently at or around the centre of the
disc. If multiple apertures are used, they may be spread
evenly on the disc or around the centre, and each individual
aperture may be different in size and shape to the others.
The disc may be made of a plurality of layers of fibres, at
least one layer being of micro-fine fibres of 0.5 to 10
microns in diameter.
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The aperture or apertures act as a flow opening and are
0.1 mm to 3.0 mm in diameter with a combined to.al opening
area of 0.1 mm2 to 10 mm2. The layer of micro-fine fibres
has a packing density of 0.05 to 0.3 and the thickness of
said layer is between 0.5 mm and 4 mm.
The advantages of this type of filter construction are
set out in the specifications referred to and provide a more
even puff-by-puff "tar" delivery profile. The present
invention takes advantage of this filter characteristic to
enable an even smoke to be provided by using the multi-part
cigarette rod construction.
Figure 11 shows another alternative construction of the
kind set forth in European Patent Application No. 89310421.6
(Publication No. 0 364 253). In this construction the
filter element comprises a barrier tube 31, an outer tube in
the form of a plug wrap 33 and the space between the tube 31
and the plug wrap 33 being filled with a porous material 34
such as cellulose acetate tow, or polypropylene tow,
polymeric foam materials or any suitable granular materials,
apertures can be provided if desired at any convenient
location. One end of the tube is blocked for gas flow as
indicated by reference numeral 36.
The tube 31 is made from a layer of micro-fine fibres
between 0.5 to 10 microns in diameter of a plurality of
filters of fibres, at least one layer being of micro-fine
fibres of 0.5 to 10 microns in diameter. The fibres have a
packing density of 0.05 to 0.3 and the thickness of the
layers between 0.5 mm and 2 mm.
The barrier tube 31 is wrapped around a core 38 made of
porous material, preferably with minimum flow resistance to
gas flow. Commonly known filter materials such as the
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cellulose acetate or polypropylene tow may be used.
Preferably the tow used may consist of a coarse fibre such
as 5 denier per filament or larger. In addition the filter
material should be packed with a low packing density.
As mentioned above apertures, similar to aperture 7 in
Figures 1 to 8, can be provided as this prevents the micro-
fine fibres in the tube becoming clogged, the flow openings
allowing what is in effect a controlled leakage.
The advantages of this type of filter are set forth in
the European Patent Specification referred to and it will be
appreciated that in any of the other constructions described
in that specification can be utilised in the present
invention.
Filters disclosed in PCT Patent Application CA/90/00070
can also be used and the disclosure in that Patent
Specification is incorporated herein. There are particular
advantages with this type of filter as with the filter shown
in Figures 11 and 12 in view of their high filtration
efficiency. This high efficiency makes it possible to use
very strong tobaccos in the region of the kindled end 10 of
the cigarette without providing untoward levels of smoke to
the smoker in the early puffs. Consequently differences in
strength between the kindled end and the other end of the
cigarette rod are able to be increased to promote the
flattening of the puff-by-puff profile.
The use of demarcated zones of different tobaccos in
the tobacco rod in conjunction with the filters of the kind
set forth which provide progressive filtering, leads to a
much more uniform puff-by-puff smoke delivery than in the
case of either a cigarette with a standard type of filter
but with different demarcated zones of different tobacco or
2~21! 9~
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cigarette filters of the kind set forth in the Patent
Specifications referred to alone. Thus the present
invention provides a particular advantageous effect by the
combination of the special filters and the demarcated zone
tobacco rod which produces a smokable cigarette which is
much more acceptable to the smoker than would be expected.
