Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Ventilated Smoking article
Field
The invention relates to a smoking article and a method of manufacture of a
smoking article.
Background
As used herein, the term "smoking article" includes smokable products such as
cigarettes, cigars
and cigarillos whether based on tobacco, tobacco derivatives, expanded
tobacco, reconstituted
tobacco or tobacco substitutes and also heat-not- burn products (i.e. products
in which flavour
is generated from a smoking material by the application of heat without
causing combustion of
the material). Typically, smoking articles are provided with filters for
removing constituents
from the smoke.
It can be desirable to introduce ventilating air into the smoke. Known ways of
doing so involve
providing ventilation holes in the outside of the filter. The ventilation
holes can be provided
relatively straightforwardly but have various disadvantages including, for
example, that they are
prone to being accidentally blocked by the user's fingers. It is also known to
provide grooves in
the filter for smoke or ventilating air flow. However, smoking articles
including grooved filters
can be complex and expensive to manufacture.
Summary
The invention provides, in a first aspect, a smoking article comprising a
source of smokable
material, a filter, a first layer surrounding at least a part of the filter, a
second layer surrounding
at least a part of the first layer and one or more paths for ventilating air
flow between the first
and second layers, wherein: (a) at least a part of the one or more paths is
located further from
an axis of the smoking article than any part of the source of smokable
material; (b) at least a
part of the first layer comprises an irregular outer surface that defines,
together with the second
layer, the one or more paths; (c) the first layer comprises a part with a
smooth inner surface that
surrounds a part of the source of smokable material or surrounds adjacent
parts of the source
of smokable material and of the filter; and, (d) the one or more paths have
one or more air
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inlets that are located near to or beyond an end of the filter nearest to the
source of smokable
material, the one or more air inlets defined by extents of the first and the
second layers towards
or beyond the end of the filter.
3 Thus, the invention can provide an effective and efficient way of
including paths for ventilating
air flow in a smoking article, namely between a first layer, which is also for
attaching the filter to
the source of smoking material, and a surrounding second layer.
The one or more paths may have one or more air outlets located near to the end
of the filter
furthest from the source of smokable material. The one or more paths may have
one or more
air outlets into the filter. The first layer and/ or the second layer may be
formed from a sheet
material.
The invention provides, in a second aspect, a method of manufacturing a
smoking article, the
13 method comprising providing a source of smokable material, providing a
filter, surrounding at
least a part of the filter with a first layer, surrounding at least a part of
the first layer with a
second layer, and forming one or more paths for ventilating air flow between
the first and
second layers, wherein: (a) at least a part of the one or more paths is
located further from an
axis of the smoking article than any part of the source of smokable material;
(b) at least a part of
the first layer comprises an irregular outer surface that defines, together
with the second layer,
the one or more paths; (c) the first layer comprises a part with a smooth
inner surface that
surrounds a part of the source of smokable material or surrounds adjacent
parts of the source
of smokable material and of the filter; and, (d) the one or more paths have
one or more air
inlets that are located near to or beyond an end of the filter nearest to the
source of smokable
material, the one or more air inlets defined by extents of the first and the
second layers towards
or beyond the end of the filter.
Brief description of the drawings
Embodiments of the present invention will now be described, by way of example
only, with
reference to the accompanying drawings, in which:
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Figure 1 is a partially-cut-away perspective view of a smoking article
according to a
first embodiment of the invention;
Figure 2 is an end view of the mouth end of the smoking article of Figure 1;
Figure 3 is a sectional view of the smoking article of Figures 1 along the
line A-A' of
Figure 2;
Figure 4 is a plan view of an element used to form the inner covering layer of
the
smoking article of Figure 1;
Figure 5 is a partially-cut-away perspective view of a smoking article
according to a
second embodiment of the invention;
Figure 6 is a sectional view of the smoking of Figure 5;
Figure 7 is a plan view of an element used to form the inner covering layer of
the
smoking article of Figure 5.
Detailed description
First embodiment
Figures 1, 2 and 3 show a smoking article 10 according to a first embodiment
of the
invention. The smoking article 10 includes a source of smokable material,
which is
preferably tobacco, in the form of a tobacco rod 11. The smoking article 10
further
includes a filter 12 co-axially attached to the tobacco rod 11. An inner
covering
layer 13 is provided around the filter 12 and around a length of the tobacco
rod 11.
An outer covering layer 14 is provided around the inner covering layer 13. One
or
more channels 15 are formed between the inner and the outer covering layers
13,
14. The one or more channels 15 form one or more paths for the flow of
ventilating air from the vicinity of the end of the filter 12 which is nearest
to the
tobacco rod 11 towards the other end of the filter 12. The end of the filter
12
nearest to the tobacco rod 11 will be referred to hereinafter as the "tobacco
end" of
the filter 12. The other end of the filter 12 will be referred to hereinafter
as the
"mouth end" of the filter 12.
The tobacco rod 11 and the filter 12 are preferably both cylindrical and
preferably
both have substantially the same outer diameter. The filter 12 includes
filtration
material, preferably surrounded by a sheet material, e.g. plugwrap (not
shown). The
plugwrap is preferably porous, i.e. permeable to fluid flow, but may be non-
porous.
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The filtration material is preferably cellulose acetate tow, bonded together
with a
plasticiser. The filtration material is preferably homogeneous. The term
"homogenous" is used to mean that the filtration material is substantially
uniform
throughout the filter 12. The filter 12 may include an additive such as a
smoke
modifying agent, e.g. activated charcoal. The filter 12 is preferably a
standard filter
but may be any other type of filter, e.g. a composite filter.
The inner covering layer 13 preferably encircles, at least once, the whole
length of
the filter 12 and a length of the tobacco rod 11 adjacent to the filter 12.
The inner
covering layer 13 is preferably adhered to and/or secured around the filter 12
and
the tobacco rod 11, as will be described in more detail below. The inner
covering
layer 13 is preferably formed from a sheet material, which is preferably a
paper. In
some embodiments, the sheet material is made of a non-porous plug wrap which
has longer fibre lengths and is more resistant to cracking or splitting when
embossed. Alternatively, the inner covering layer 13 may be formed from a
relatively thick tipping paper or any type of tipping paper or any other
suitable
material, such as a plastics material, a metal foil or a metallised paper. The
inner
covering layer 13 is preferably substantially non-porous, i.e. impermeable to
fluid
flow.
The inner covering layer 13 preferably forms an elongate cylindrical tube
which is
longitudinally divided into an irregular portion 13a and a regular portion
13b. The
portions 13a and 13b are preferably formed from a single piece of the sheet
material.
The regular portion 13b of the inner covering layer 13 preferably encircles,
at least
once, a length of the filter 12 adjacent to the tobacco rod 11 and an adjacent
length
of the tobacco rod 11. The regular portion 13b is preferably adhered, at least
in
part, to the outer surfaces of the lengths of the filter 12 and the tobacco
rod 11.
The inner covering layer 13 is also preferably secured around the lengths of
the
filter 12 and the tobacco rod 11 by a longitudinal seam of adhesive joining
opposite
edges. Hence the regular portion 13b joins the filter 12 to the tobacco rod 11
and
also helps to form a seal against ingress of external air into the tobacco end
of the
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filter 12 during use, i.e. when the user draws on the smoking article 10.
Since the
inner surface of the regular portion 13b of the inner covering layer 13 and
the outer
surfaces of the filter 12 and the tobacco rod 11 are all preferably smooth,
this can
help to provide a good join and a good seal.
The irregular portion 13a of the inner covering layer 13 preferably encircles,
at least
once, the length of the filter 12 that is not encircled by the regular portion
13b.
Hence the irregular portion 13a preferably extends to the mouth end of the
filter 12.
However, the irregular portion 13a need not extend to, or may extend beyond,
the
mouth end of the filter 12. The irregular portion 13a is preferably secured
around
the filter 12 by a longitudinal seam of adhesive joining opposite edges. The
irregular portion 13a is also preferably adhered, at least in part, to the
outer surface
of the filter 12.
The irregular portion 13a of the inner covering layer 13 is shaped so as to
define, in
combination with the outer covering layer 14, the one or more channels 15.
The channels 15 are adapted to deliver ventilating air from near to the
tobacco end
of the filter 52 to near to the mouth end of the filter 12. The ventilating
air is from
the atmosphere around the smoking article 10. The ventilating air that is
delivered
to the mouth end of the filter 12 mixes with, and thus dilutes, the smoke
which is
drawn through the tobacco rod 11 and the filter 12. The mixing takes place
outside
the smoking article 10, e.g. in the user's mouth. The channels 15 preferably
each
have one or more air inlets 16 near to the tobacco end of the filter 12 and
one or
more air outlets 17 near to the mouth end of the filter 12.
The irregular portion 13a preferably has a corrugated outer surface,
particularly a
surface having one or more elongate grooves 18 separated by ridges 19. The
ridges
19 are preferably raised in relation to the regular portion 13b of the inner
covering
layer 13.
The grooves 18 preferably all extend substantially parallel to each other and
parallel
to the longitudinal axis of the filter 12. However, the grooves 18 may extend
in one
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or more different directions. For example, they may follow one or more helical
paths or one or more sinuous paths along the filter 12. Such paths can provide
a
way of increasing the path length and hence increasing the pressure drop along
the
path. The pressure drop along the path determines the ventilation properties,
as
will be described in more detail below.
The grooves 18 are preferably equally spaced around the circumference of the
filter
12. There are preferably between eight and ten grooves 18 spaced around the
circumference. However, there may be fewer grooves 18, e.g. one, two, or four
grooves 18, or more grooves 18, e.g. eighteen or thirty-six grooves 18. The
grooves
18 are preferably spaced around the whole circumference of the filter 12 but
may be
spaced around one or more parts of the circumference.
The ridges 19 and the grooves 18 preferably each have a pointed profile so as
to
form a triangular or sawtooth overall profile. However, the profile of the
ridges 19
and/or the grooves 18 may be different. For example, the ridges 19 and the
grooves 18 may both be curved, thereby forming a sinuous overall profile. The
ridges 19 may be pointed and the grooves 18 may be curved or vice versa,
thereby
forming a fluted overall profile. The ridges 19 and/or the grooves 18 may
include
one or more substantially flat portions. For example, they may form a
castellated
overall profile. The ridges 19 and the grooves 18 preferably have a constant
profile
but may have a profile which varies along the length and/or around the
circumference of the filter 12. For example, the width of the grooves 18 may
increase or decrease gradually towards the mouth end of the filter 12.
The width of the grooves 18 and the height of the grooves 18 are preferably
selected so as to provide the desired ventilation, as will be described in
more detail
below.
The outer covering layer 14 preferably encircles, at least once, the whole
length of
the inner covering layer 13. However, the outer covering layer 14 need not
extend
to, or may extend beyond, one or both ends of the inner covering layer 13. The
outer covering layer 14 is preferably formed from a sheet material, which is
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preferably a standard tipping paper. However, the outer covering layer 14 may
be
formed from any suitable material, such as a plastics material, a metal foil
or a
metallised paper. The outer covering layer 14 is preferably substantially non-
porous.
The outer covering layer 14, in combination with the inner covering layer 13,
defines the one or more channels 15. The outer covering layer 14 preferably
forms
a substantially smooth cylindrical tube around the inner covering layer 13. In
particular, the outer covering layer 14 preferably forms a substantially
smooth
cylindrical tube enveloping the ridges 19 (or other protrusions) provided on
the
irregular portion 13a of the inner covering layer. Thus, channels 15a1, 15a2,
..., 15an
are formed in the spaces between the inner and the outer covering layers 13,
14, in
the grooves 18 in the irregular portion 13a of the inner covering layer 13. An
annular space 15b is also formed between the inner and the outer covering
layers
13, 14 where the outer covering layer 14 extends over the regular portion 13b
of the
inner covering layer 13.
The channels 15a preferably have respective outlets 17 at their ends nearest
to the
mouth end of the filter 12. The inner and the outer covering layers 13, 14
preferably both extend to the end of the filter 12 and so the outlets 17 are
preferably located at the end of the filter 12. However, the inner and/or the
outer
covering layers 13, 14 may have different extents, as described above, and so
the
outlets 17 may have different locations. Nevertheless, the outlets 17 are
preferably
located such that, when the user places the smoking article 10 in the mouth,
the
outlets 17 will also be in the mouth. Thus, when the user draws on the smoking
article 10, ventilating air is drawn through the channels 15a.
The annular space 15b has an annular opening at its end away from the channels
15a. This annular opening forms an inlet 16 for the ventilating air. The
annular
space 15b is also in fluid communication with each of the channels 15a.
However,
the outer covering layer 14 need not extend over the regular portion 13b of
the
inner covering layer 13 and so there may be no annular space. In this case,
the
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channels 15a have respective inlets 16 for ventilating air which are located
where the
outer covering layer 14 ends.
The outer covering layer 14 is preferably secured around the inner covering
layer 13
by a longitudinal seam of adhesive joining opposite edges. The outer covering
layer
14 is also preferably adhered, at least in part, to the ridges 19 (or other
protrusions)
provided on the irregular portion 13a of the inner covering layer 13.
Instead of the corrugated outer surface described above, the irregular portion
13a of
the inner covering layer 13 may have any shape which, in combination with the
outer covering layer 14, forms the channels 15 between the inner and the outer
covering layers 13, 14. For example, the irregular portion 13a may include
isolated
protrusions upon which the outer covering layer 14 lies, thereby forming air
flow
paths in the regions between the protrusions.
In use, when the user draws on the smoking article 10, smoke and air is drawn
through the tobacco rod 11 and then the filter 12, and ventilating air is
drawn
through the channels 15.
The properties of the channels 15 are preferably selected so as to provide the
desired ventilation. In particular, the draw resistance of the channels 15 is
determined by, amongst other things, their number, cross-sectional area,
length and
shape. For example, a larger number of channels 15 and/or larger channels 15
will
have a smaller resistance to the flow of air. This resistance is preferably
selected, in
relation to the flow resistance through the tobacco rod 11 and the filter 12,
so as to
provide the desired ventilation. For example, if the resistance of the
channels 15 is
lower in relation to the resistance of the tobacco rod 11 and the filter 12,
then the
amount of air drawn through the channels 15 in relation to the amount of smoke
and air drawn through the filter 12 will be higher and so the smoke will be
more
diluted. Conversely, if the resistance of the channels 15 is higher in
relation to the
resistance of the tobacco rod 11 and the filter 12, then the amount of air
drawn
through the channels 15 in relation to the amount of smoke and air drawn
through
the filter 12 will be lower and so the smoke will be less diluted.
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The smoking article 10 can have the advantage that the inlets 16 for
ventilating air
are less likely to be occluded by the user's fingers. The inlets 16 are
preferably
positioned near to the tobacco end of the filter 12, or even beyond the
tobacco end
of the filter 12, and so are away from usual holding position of the user's
fingers.
Furthermore, the inlets 16 are preferably orientated such that they face
longitudinally along the smoking article 10 and so, even if the fingers are
positioned
near to the inlets 16, the fingers are still unlikely to occlude the inlets
16. In
contrast, known smoking article including a plurality of vent holes in the
tipping
paper can have the disadvantage that the vent holes can be relatively easily
occluded
by the user's fingers. This can have a negative effect on the consistency of
the
smoke which is delivered to the user.
The smoking article 10 can also have the advantage of providing more effective
filtration performance. This is because the ventilating air is mixed with the
smoke
outside the filter 12. In contrast, known smoking articles in which the
ventilating
air is introduced into the filter 12 can have the disadvantage that the
introduced
ventilating air increases the flow rate towards the mouth end of the filter
12, and
therefore reduces the residence time of the smoke. This can have a negative
effect
on the filtering performance.
Because the filter 12 is preferably completely covered by the inner and the
outer
covering layers 13, 14, the smoking article 10 can also have the advantage
that a
reduced amount of smoke will come into contact with the user's fingers. This
is
because the inlets are away from usual holding position of the user's fingers.
In
contrast, in known smoking articles including a plurality of vent holes in the
tipping
paper, smoke can exit the vent holes and come into contact with the user's
fingers,
e.g. when the user is not drawing on the smoking article.
Figure 4 shows a sheet 40 for forming the inner covering layer 13 of the
smoking
article 10. The sheet is preferably formed from a standard tipping paper, as
described above. The sheet is preferably rectangular and is divided into two
rectangular portions, namely an irregular portion 40a and a regular portion
40b.
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The irregular portion 40a corresponds to the irregular portion 13a of the
inner
covering layer 13. The regular portion 40b corresponds to the regular portion
13b
of the inner covering layer 13.
The irregular portion 40a has a profile as described above in relation to the
irregular
portion 13a of the inner covering layer. The profile preferably has a
plurality of
raised pointed ridges 41, as described above. The raised pointed ridges 41
preferably each have an oblique, triangular side wall 42 at their ends nearest
to the
regular portion 40b of the sheet 40. However, the sidewall 42 may be
substantially
perpendicular to the regular portion 40b of the sheet 40 and/or may have a
different shape.
The profile of the irregular portion 40a of the sheet 40 is preferably formed
by
embossing. The embossing is preferably carried out using methods which will be
known per se to persons skilled in the art. However, the profile may be formed
using a method other than embossing. For example, if the sheet 40 is formed
from
a plastics material, then this may be moulded to form the profile. The whole
thickness of the sheet 40 is preferably formed into the corrugations or
irregularities
41. Hence the top and bottom surfaces of the sheet 40 will both have a
similar,
irregular profile. This is particularly suitable where the sheet 40 is formed
from a
tipping paper. However, the corrugations or irregularities 41 may be formed
only
towards the top surface of the sheet 40, and the bottom surface of the sheet
may be
substantially smooth. This is particularly suitable where the sheet 40 is
formed
from a relatively thick material.
The smoking article 10 can be manufactured using a method in which the tobacco
rod 11 is joined to the filter 12 by means of the inner covering layer 13,
which is
preferably adhered to and/or secured around the filter 12 and the tobacco rod
11,
as described above. The sheet 40 for forming the inner covering layer 13 is
preferably embossed (or otherwise shaped) prior to being wrapped around the
filter
12 and the tobacco rod 11. The outer covering layer 14 is then preferably
wrapped
around and adhered to and/or secured around the inner covering layer 13.
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The smoking article 10 can also be manufactured using a method in which two
tobacco rods 11 are simultaneously joined to each end of a double length of
the
filter 12 and the resulting article is then cut into two halves to form two
smoking
articles 10. In this case, a double length of the sheet 40 for forming the
inner
covering layer 13 and a double length of a sheet for forming the outer
covering
layer 14 are preferably used. The double length of the sheet 40 for forming
the
inner covering layer 13 preferably has the regular portion 40b at either end
and an
intermediate double length of the irregular portion 40a.
A sheet having a symmetrical arrangement of regular and irregular portions is
generally preferable since the sheet can be wrapped more effectively, for
example
without the slewing or creasing that can occur when a sheet having a non-
symmetric
arrangement is used
The smoking article 10 can be manufactured efficiently because its formation
preferably largely consists of wrapping layers of sheet material around the
filter 12
and the tobacco rod 11 and because the wrapping processes themselves can be
carried out efficiently. Furthermore, the smoking article 10 can be
manufactured
using methods and apparatuses which are based upon existing methods and
apparatuses. The apparatus may include first and second tipping sections for
providing the inner and outer covering layers 13, 14 respectively.
Second embodiment
Figures 5 and 6 show a smoking article 50 according to a second embodiment of
the
invention. The smoking article 50 includes a source of smokable material,
which is
preferably tobacco, in the form of a tobacco rod 51. The smoking article 50
further
includes a filter 52 co-axially attached to the tobacco rod 51. The filter 52
is
longitudinally divided into two filter parts, namely a mouth-end filter part
52a and a
tobacco-end filter part 52b. An inner covering layer 53 is provided around the
filter
52 and around a length of the tobacco rod 51. An outer covering layer 54 is
provided around the inner covering layer. One or more channels 55 are formed
between the inner and the outer covering layers 53, 54. The one or more
channels
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55 form one or more paths for the flow of ventilating air from near to the
tobacco
end of the filter to one or more intermediate locations in the filter.
The tobacco rod 51 and the two filter parts 52a, 52b are preferably all
cylindrical.
The tobacco rod 51 and the tobacco-end filter part 52b preferably have
substantially
the same outer diameter. The mouth-end filter part 52a preferably has a
slightly
larger outer diameter than the tobacco-end filter part 52b, as will be
described in
more detail below. The two filter parts 52a, 52b each include filtration
material,
preferably surrounded by a sheet material, e.g. plugwrap (not shown). The
plugwrap
is preferably porous, but may be non-porous. The plugwrap need not be
included.
The filtration material is preferably cellulose acetate tow, bonded together
with a
plasticiser. The filtration material is preferably homogeneous. The term
"homogenous" is used to mean that the filtration material is substantially
uniform
throughout the filter 52. The mouth-end and/or tobacco-end filter parts 52a,
52b
may include an additive such as a smoke modifying agent, e.g. activated
charcoal.
The two filter parts 52a, 52b may include different filtration materials, may
be
surrounded by different materials and may include different additives.
The inner covering layer 53 preferably encircles, at least once, the whole
length of
the tobacco-end filter part 52b and an adjacent length of the tobacco rod 51.
The
inner covering layer 53 is preferably adhered to and/or secured around the
tobacco-
end filter part 52b and the tobacco rod 51, as will be described in more
detail below.
The inner covering layer 53 is preferably formed from a sheet material, which
is
preferably a paper. In some embodiments, the sheet material is made of a non-
porous plug wrap which has longer fibre lengths and is more resistant to
cracking or
splitting when embossed. Alternatively, the inner covering layer 53 may be
formed
from a relatively thick tipping paper or any type of tipping paper or any
other
suitable material, such as a plastics material, a metal foil or a metallised
paper. The
inner covering layer 53 is preferably substantially non-porous.
The inner covering layer 53 preferably forms an elongate cylindrical tube
which is
longitudinally divided into an irregular portion 53a and a regular portion
53b. The
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portions 53a and 53b are preferably formed from a single piece of the sheet
material.
The regular portion 53b of the inner covering layer 53 preferably encircles,
at least
once, a length of the tobacco-end filter part 52b adjacent to the tobacco rod
51 and
an adjacent length of the tobacco rod 51. The regular portion 53b is
preferably
adhered, at least in part, to the outer surfaces of the lengths of the tobacco-
end
filter part 52b and the tobacco rod 51. The regular portion 53b is also
preferably
secured around the lengths of the tobacco-end filter part 52b and the tobacco
rod
51 by a longitudinal seam of adhesive joining opposite edges. Hence the
regular
portion 53b joins the tobacco-end filter part 52b to the tobacco rod 51 and
also
helps to form a seal against ingress of external air into the tobacco end of
the filter
52. Since the inner surface of the regular portion 53b of the inner covering
layer 53
and the outer surfaces of the tobacco-end filter part 52b and the tobacco rod
51 are
all preferably smooth, this can help to provide a good join and a good seal.
The irregular portion 53a of the inner covering layer 53 preferably encircles,
at least
once, the length of the tobacco-end filter part 52b that is not encircled by
the
regular portion 53b. The two filter parts 52a, 52b preferably have a similar
length
and hence the inner covering layer 53 preferably extends to around halfway
between
the tobacco end and the mouth end of the filter 52. For example, the filter 52
may
be 27 mm in length and the irregular portion 53a may extend to a distance of
13 mm from the mouth end of the filter 52. However, the mouth-end filter part
52a, tobacco-end filter part 52b and/or the irregular portion 53a may have
different
lengths. Also, the edge of the irregular portion 53a nearest to the mouth end
of the
filter 52 may be obliquely angled and/or non-straight and hence the extent of
the
irregular portion 53a towards the mouth end of the filter 52 may vary around
the
circumference of the filter 52. As will be described below, the extent of the
irregular portion 53a determines the extent of the channels 55 and hence the
location(s) at which the ventilating air is introduced into the filter 52. The
irregular
portion 53a is preferably secured around the tobacco-end filter part 52b by a
longitudinal seam of adhesive joining opposite edges. The irregular portion
53a is
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also preferably adhered, at least in part, to the outer surface of the tobacco-
end
filter part 52b.
The irregular portion 53a of the inner covering layer 53 is shaped so as to
define, in
combination with the outer covering layer 54, the one or more channels 55.
The channels 55 are adapted to deliver ventilating air from near to the
tobacco end
of the filter 52 to one or more intermediate locations in the filter 52. The
one or
more intermediate locations are preferable in the vicinity of where the filter
part
52a, 52b meet. The ventilating air that is delivered to the intermediate
locations
enters the filter 52 and mixes with, and thus dilutes, the smoke which is
drawn
through the tobacco rod 51 and the filter 52. The mixing takes place mainly in
the
filter 52. The channels 55 preferably each have one or more air inlets 56 near
to the
tobacco end of the filter 52 and one or more air outlets 57 at the
intermediate
locations in the filter 52.
The irregular portion 53a preferably has a corrugated outer surface,
particularly a
surface having one or more elongate grooves 58 separated by ridges 59. The
ridges
59 are preferably raised in relation to the regular portion 53b of the inner
covering
layer 53.
The grooves 58 preferably all extend substantially parallel to each other and
parallel
to the longitudinal axis of the filter 52. However, the grooves 58 may extend
in one
or more different directions. For example, they may follow one or more helical
paths or one or more sinuous paths along the filter 52. Such paths can provide
a
way of increasing the path length and hence increasing the pressure drop along
the
path.
The grooves 58 are preferably equally spaced around the circumference of the
filter
12. There are preferably between eight and ten grooves 58 spaced around the
circumference. However, there may be fewer grooves 58, e.g. one, two, or four
grooves 58, or more grooves 58, e.g. eighteen or thirty-six grooves 58. The
grooves
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58 are preferably spaced around the whole circumference of the filter 52 but
may be
spaced around one or more parts of the circumference.
The ridges 59 and the grooves 58 preferably each have a pointed profile so as
to
form a triangular or sawtooth overall profile. However, the profile of the
ridges 59
and/or the grooves 58 may be different. For example, the ridges 59 and the
grooves 58 may both be curved, thereby forming a sinuous overall profile. The
ridges 59 may be pointed and the grooves 58 may be curved or vice versa,
thereby
forming a fluted overall profile. The ridges 59 and/or the grooves 58 may
include
one or more substantially flat portions. For example, they may form a
castellated
overall profile. The ridges 59 and the grooves 58 preferably have a constant
profile
but may have a profile which varies along the length and/or around the
circumference of the filter 52. For example, the width of the grooves 58 may
increase or decrease gradually towards one end.
The width of the grooves 58 and the height of the grooves 58 are preferably
selected so as to provide the desired ventilation, as will be described in
more detail
below.
The outer covering layer 54 preferably encircles, at least once, the whole
length of
the inner covering layer 53 and the whole length of the mouth-end filter part
52.
Hence the outer covering layer 54 preferably extends to the mouth end of the
filter
52. However, the outer covering layer 54 may extend further or less than this.
The
outer covering layer 54 is preferably formed from a sheet material, which is
preferably a tipping paper. However, the outer covering layer 54 may be formed
from any suitable material, such as a plastics material, a metal foil or a
metallised
paper. The outer covering layer 54 is preferably substantially non-porous.
The outer covering layer 54, in combination with the inner covering layer 53,
defines the one or more channels 55. The outer covering layer 54 preferably
forms
a substantially smooth cylindrical tube around the inner covering layer 53 and
the
length of the filter 52 not encircled by the inner covering layer 53. In
particular, the
outer covering layer 54 preferably forms a substantially smooth cylindrical
tube
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enveloping the ridges 59 (or other protrusions) in the irregular portion 53a
of the
inner covering layer. Thus, channels 55a1, 55a2, ..., 55aõ are formed in the
spaces
between the inner and the outer covering layers 53, 54, in the grooves 58 in
the
irregular portion 53a of the inner covering layer. An annular space 55b is
also
formed between the inner and the outer covering layers 53, 54 where the outer
covering layer 54 extends over the regular portion 53b of the inner covering
layer
53. The outer covering layer 54 also fits closely around the mouth-end filter
part
52a. The outer diameter of the mouth-end filter part 52a is preferably
substantially
the same as the diameter of the cylinder that envelopes the irregular portion
53a of
the inner covering layer 53. Thus, the outer covering layer 54 extends
smoothly
between the irregular portion 53a of the inner covering layer 53 and the mouth-
end
filter part 52a.
The extent of the channels 55a towards the mouth end of the filter 52 is
preferably
determined by the extent of the irregular portion 53a of the inner covering
layer 53,
as described above. The irregular portion 53a and hence the channels 55a
preferably end at one or more intermediate locations in the filter 52,
preferably in
the vicinity of where the two filter parts 52a, 52b meet. The channels 55a
preferably have respective outlets 57 at their ends at the intermediate
locations.
Because the outer covering layer 54 fits closely around the length of the
filter 52 not
encircled by the inner covering layer 53, ventilating air exiting the outlets
57 is
directed into the interior of the filter 52 and, in particular, into the
interior of the
mouth-end filter part 52a.
The annular space 55b has an annular opening at its end towards the tobacco
end of
the filter 52. This annular opening forms an inlet 56 for the ventilating air.
The
annular space 55b is also in fluid communication with each of the channels
55a.
However, the outer covering layer 54 need not extend over the regular portion
53b
of the inner covering layer 53 and so there may be no annular space. In this
case,
the channels 55a have respective inlets 56 for ventilating air which are
located where
the outer covering layer 54 ends.
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The outer covering layer 54 is preferably secured around the inner covering
layer 53
by a longitudinal seam of adhesive joining opposite edges. The outer covering
layer
54 is also preferably adhered, at least in part, to the ridges 59 (or other
protrusions)
provided on the irregular portion 53a of the inner covering layer 53.
Instead of the corrugated outer surface described above, the irregular portion
53a of
the inner covering layer 53 may have any shape which, in combination with the
outer covering layer 54, forms the channel between the inner and the outer
covering
layers 53, 54. For example, the irregular portion 53a may include isolated
protrusions upon which the outer covering layer 54 lies, thereby forming air
flow
paths in the regions between the protrusions.
In use, when the user draws on the smoking article 50, smoke and air is drawn
through the tobacco rod 51 and then the filter 52, and ventilating air is
drawn
through the channels 55 and then a length of the filter 52.
The properties of the channels 55 are preferably selected so as to provide the
desired ventilation. In particular, the draw resistance of the channels 55 is
determined by, amongst other things, their number, cross-sectional area,
length and
shape. This resistance and hence the pressure drop is preferably chosen to
provide
the desired ventilation. The locations of the outlets 57 of the channels 55a,
i.e., the
distance from either end of the filter 52, can also be selected to provide
desired
characteristics for the filter 52, e.g. filtering and dilution
characteristics.
The smoking article 50 can have the advantage that the inlets 56 for
ventilating air
are much less likely to be occluded by the user's fingers as described above
in
relation to the first embodiment.
Figure 7 shows a sheet 70 for forming the inner covering layer 53 of the
smoking
article 50. The sheet 70 is preferably formed from a standard tipping paper,
as
described above. The sheet 70 is preferably rectangular and is divided into
two
rectangular portions, namely an irregular portion 70a and a regular portion
70b.
The irregular portion 70a corresponds to the irregular portion 53a of the
inner
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covering layer 53. The regular portion 70b corresponds to the regular portion
53b
of the inner covering layer 53.
The irregular portion 70a has a profile as described above in relation to the
irregular
portion 53a of the inner covering layer. The profile preferably has a
plurality of
raised pointed ridges 71, as described above. The raised pointed ridges 71
preferably each have an oblique, triangular side wall 72 at their ends nearest
to the
regular portion 70b of the sheet 70. However, the sidewall 72 may be
substantially
perpendicular to the regular portion 70b of the sheet 70 and/or may have a
different shape.
The profile of the irregular portion 70a of the sheet is preferably formed by
embossing. The embossing is preferably carried out using methods which will be
known per se to persons skilled in the art. However, the profile may be formed
using a method other than embossing. For example, if the sheet 70 is formed
from
a plastics material, then this may be moulded to form the profile. The whole
thickness of the sheet 70 is preferably formed into the corrugations or
irregularities
71. Hence the top and bottom surfaces of the sheet 70 will both have a
similar,
irregular profile. This is particularly suitable where the sheet 70 is formed
from a
tipping paper. However, the corrugations or irregularities may be formed only
towards the top surface of the sheet 70, and the bottom surface of the sheet
70 may
be substantially smooth. This is particularly suitable where the sheet 70 is
formed
from a relatively thick material.
The smoking article 50 can be manufactured using a method in which the tobacco
rod 51 is joined to the tobacco-end filter part 52b by means of the inner
covering
layer 53, which is preferably adhered to and/or secured around the tobacco-end
filter part 52b and the tobacco rod 51, as described above. The sheet 70 for
forming the inner covering layer 53 is preferably embossed (or otherwise
shaped)
prior to being wrapped around the filter 52 and the tobacco rod 51. The mouth-
end
filter part 52a is then joined to the tobacco-end filter part 52b and tobacco
rod 51
by means of the outer covering layer 54, which is preferably wrapped around
and
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adhered to and/or secured around the tobacco-end filter part 52a and the inner
covering layer 53.
The smoking article 50 can be manufactured using a method in which two tobacco
rods 51 are simultaneously joined to each end of a double length of the
tobacco-end
filter part 52b. A double length of the sheet 70 for forming the inner
covering layer
53 is preferably used. The sheet preferably has the regular portion 70b at
either end
and an intermediate double length of the irregular portion 70a. The resulting
article is then cut into two halves. The tobacco-end filter part 52 may be
joined to
each half as described above. Alternatively, the two halves may be
simultaneously
joined to each end of a double length of the tobacco-end filter part 52a. A
double
length of a sheet for forming the outer covering layer 54 is preferably used.
The
resulting article is then cut into two halves to form two smoking articles 50.
The smoking article 50 can be manufactured efficiently because its formation
preferably largely consists of wrapping layers of sheet material around the
two filter
parts 52a, 52b and the tobacco rod 51 and because the wrapping processes
themselves can be carried out efficiently. Furthermore, the smoking article 50
can
be manufactured using methods and apparatuses which are based upon existing
methods and apparatuses. The apparatus may include first and second tipping
sections for providing the inner and outer covering layers 53, 54
respectively. The
two filter parts 52a, 52b and the separate wrapping thereof can allow the
sheet 70
for forming the inner covering layer 53 to be positioned more easily and can
also
enable a double length of the sheet 70 to be used in the 'two-up'
manufacturing
method described above.
Further embodiments
It should be realised that the hereinbefore described example embodiments
should
not be construed as limiting. Other variations and modifications will be
apparent to
persons skilled in the art upon reading the present application.
The regular portion 13b, 53b of the inner covering layer 13, 53 may only
encircle a
length of the tobacco rod 11, 51, rather than lengths of the filter 12, 52 and
the
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tobacco rod 11, 51. The regular portion 13b, 53b is preferably adhered to and
secured around the length of the tobacco rod 11, 51. This can still help to
form a
good seal against air ingress between the inner covering layer 13, 53 and the
tobacco
rod 11, 51. In this case, the irregular portion 13a, 53a of the inner covering
layer
13, 53 is preferably adhered to the filter 12, 52 to join the filter 12, 52 to
the
tobacco rod 11, 51.
The inner covering layer 13, 53 need not include the regular portion 13b, 53b
and so
may consist of only the irregular portion 13a, 53a. In this case, the
irregular portion
13a, 53a preferably joins together, and forms a seal between, the filter 12,
52 and
the tobacco rod 11, 51. If the inner surface of the irregular portion 13a, 53a
is
smooth, then a good seal can be achieved by adhering and/or securing as
described
above in relation to the regular portion 13b, 53b. If the inner surface of the
irregular portion 13a, 53a is not smooth, e.g. because the inner covering
layer 13, 53
is formed from an embossed tipping paper, then further modifications may be
needed to help to achieve a good seal. For example, a relatively thick layer
of
adhesive may be provided between the inner covering layer 13, 53 and the
tobacco
rod 11, 51 for bridging the spaces therebetween.
Instead of the smooth cylindrical shape described above, the filter 12, 52 may
have
a different shape.
For example, the outer surface of the filter 12, 52 may be provided with
corrugations or irregularities to complement those provided on the inner
surface of
the irregular portion 13a, 53a of the inner covering layer 13, 53. Hence the
filter 12,
52 substantially fills the volume inside the inner covering layer 13, 53. This
can
help to avoid there being any smoke paths through the smoking article 10, 50
which
do not pass through the filtration material.
Furthermore, in relation to the second embodiment only, the filter 52 may not
be
divided into the two filter parts 52a, 52b. In this case, the filter 52
preferably has a
length with an increased diameter at its mouth end. The length preferably
starts
where the irregular portion 53a of inner covering layer 53 ends. The increased
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diameter is preferably substantially the same as the diameter of the cylinder
that
envelopes the irregular portion 53a of the inner covering layer 53. However,
the
filter 52 may have a uniform outer diameter instead. In this case, the outer
covering
layer 54 may be provided with a length with an increased thickness at its
mouth end.
Thus, the outer covering layer 54 can be wrapped around the inner covering
layer 53
and the filter 52 with less mechanical stress in the filter 52 and the layers
53, 54.
Instead of being substantially non-porous, the inner and/or the outer covering
layers 13, 14, 53, 54 may be porous. For example, they may be formed of a
porous
material and/or they may be provided with ventilation holes. Thus, in addition
to
the flow along the whole length of the channels 15, 55, ventilating air may
also be
able to enter the channels 15, 55 though the outer covering layer 14, 54
and/or exit
the channels through the inner covering layer 13, 53 into the filter 12, 52.
The
porosity of the inner and/or the outer covering layers 13, 14, 53, 54 can be
selected
to provide a smoking article 10, 50 having desired ventilation
characteristics.
The inner covering layer 13, 53 need not encircle the tobacco rod 11, 51 and
need
not be for joining the filter 12, 52 to the tobacco rod 11, 51. Instead, a
further
covering layer may be used to join the filter 12, 52 to the tobacco rod 11,
51. For
example, a further covering layer may be adhered to and/or secured around a
length
of the regular portion 13b, 53b of inner wrapping layer 13, 53 and a length of
the
tobacco rod 11, 51. Thus, in this case, the filter 12, 52 may be wrapped with
the
inner and the outer covering layers 13, 14, 53, 54 independently of the
formation of
the smoking article 10, 50.
Instead of being a substantially smooth cylindrical tube, the outer covering
layer 14,
54 may have a different shape.
For example, the outer covering layer 14, 54 may be provided with corrugations
or
other irregularities on its inner surface. These corrugations or
irregularities may be
provided instead of those in the inner covering layer 13, 53 so as to define
the
channels 15, 55. In this case, the inner covering layer 13, 53 need not be
provided
with an irregular portion 13a, 53a. Alternatively, the corrugations or
irregularities in
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the outer covering layer 14, 54 may be adapted to co-operate with those in the
inner
covering layer 13, 53 so as to define the channels 15, 55. For example, the
inner
and the outer covering layers 13, 14, 53, 54 may have a plurality of aligned
grooves
and ridges.
Furthermore, the outer covering layer 14, 54 may be provided with corrugations
or
other irregularities on its inner surface in the region where it encircles the
regular
portion 13a, 53a of the inner covering layer 13, 53. This can help to maintain
the
space between the inner and the outer covering layers 13, 14, 53, 54 in this
region
and so ensure that the flow of ventilating air into the channels 15a, 55a is
less likely
to be blocked, e.g. by deformation of the outer covering layer 14, 54 during
use.
Embodiments of the invention are configured to comply with applicable laws
and/or regulations, such as, by way of non-limiting example, regulations
relating to
flavours, additives, emissions, constituents, and/or the like.
Any of the features described in any embodiment may be used in combination
with
any other features of any other embodiment.
