U.S. patent application number 12/782443 was filed with the patent office on 2010-11-18 for smoking article with improved flow restriction element.
This patent application is currently assigned to Philip Morris USA Inc.. Invention is credited to Yves Jordil, Charles Kuersteiner, Mohammed Slasli.
Application Number | 20100288293 12/782443 |
Document ID | / |
Family ID | 41138825 |
Filed Date | 2010-11-18 |
United States Patent
Application |
20100288293 |
Kind Code |
A1 |
Slasli; Mohammed ; et
al. |
November 18, 2010 |
SMOKING ARTICLE WITH IMPROVED FLOW RESTRICTION ELEMENT
Abstract
A smoking article includes a rod of smokable material and a
filter including a flow restriction element attached to the rod of
smokable material. The flow restriction element includes a first
upstream integral tubular portion, a second downstream integral
tubular portion of substantially the same external diameter as the
first tubular portion, and a third central integral tubular portion
located between the first and second tubular portions. The third
tubular portion is of reduced external diameter compared to the
first and second tubular portions. A transverse barrier having at
least one orifice therein is disposed between a first upstream
cavity at least partially defined by an inner periphery of the
first tubular portion and a second downstream cavity at least
partially defined by an inner periphery of the second tubular
portion. A ventilation zone in communication with the second cavity
is also provided at a location along the filter.
Inventors: |
Slasli; Mohammed; (Prilly,
CH) ; Jordil; Yves; (Lugrin, FR) ;
Kuersteiner; Charles; (Jouxtens-Mezery, CH) |
Correspondence
Address: |
BUCHANAN, INGERSOLL & ROONEY PC
POST OFFICE BOX 1404
ALEXANDRIA
VA
22313-1404
US
|
Assignee: |
Philip Morris USA Inc.
Richmond
VA
|
Family ID: |
41138825 |
Appl. No.: |
12/782443 |
Filed: |
May 18, 2010 |
Current U.S.
Class: |
131/338 ;
131/361 |
Current CPC
Class: |
A24D 3/045 20130101;
A24D 3/041 20130101; A24D 3/04 20130101 |
Class at
Publication: |
131/338 ;
131/361 |
International
Class: |
A24D 3/04 20060101
A24D003/04; A24B 1/04 20060101 A24B001/04 |
Foreign Application Data
Date |
Code |
Application Number |
May 18, 2009 |
EP |
09251336.5 |
Claims
1. A smoking article comprising: a rod of smokable material; a
filter including a flow restriction element attached to the rod of
smokable material, the flow restriction element including: a first
upstream integral tubular portion; a second downstream integral
tubular portion of substantially the same external diameter as the
first tubular portion; a third central integral tubular portion
located between the first and second tubular portions, the third
tubular portion being of reduced external diameter compared to the
first and second tubular portions; and a transverse barrier having
at least one orifice provided therein, the transverse barrier being
disposed between a first upstream cavity at least partially defined
by an inner periphery of the first tubular portion and a second
downstream cavity at least partially defined by an inner periphery
of the second tubular portion; and a ventilation zone in
communication with the second cavity at a location along the
filter.
2. The smoking article of claim 1, wherein the transverse barrier
has a single substantially central orifice having a diameter
ranging from about 0.4 mm to about 0.8 mm provided therein.
3. The smoking article of claim 1, wherein the filter is attached
to the rod of smokable material by a band of tipping paper and the
ventilation zone includes at least one circumferential row of
perforations provided through a portion of the tipping paper
overlying the third tubular portion of the flow restriction
element.
4. The smoking article of claim 3, wherein the first cavity of the
flow restriction element is at least partially defined by an inner
periphery of the first and third tubular portions.
5. The smoking article of claim 4, wherein one or more openings are
provided in an upstream transverse end surface of the second
tubular portion that form a communication path between the second
cavity and the at least one circumferential row of
perforations.
6. The smoking article of claim 3, wherein the second cavity of the
flow restriction element is at least partially defined by an inner
periphery of the second and third tubular portions.
7. The smoking article of claim 6, wherein one or more openings are
provided in a circumferential surface of the third tubular portion
that form a communication path between the second cavity and the at
least one circumferential row of perforations.
8. The smoking article of claim 1, wherein the filter further
includes a first filter segment upstream of the flow restriction
element and a second filter segment downstream of the flow
restriction element.
9. The smoking article of claim 1, wherein the wrapper has a basis
weight ranging from about 35 g/m.sup.2 to about 60 g/m.sup.2, a
filler loading ranging from about 20 percent to about 50 percent by
weight, a permeability ranging from about 2 Coresta units to about
18 Coresta units, and about 0.3 percent to about 5 percent by
weight of a burn modifier.
10. The smoking article of claim 1, wherein the smoking article has
a ventilation level of at least about 50 percent, preferably of at
least about 60 percent.
11. The smoking article of claim 1, wherein the flow restriction
element is at least about 10 mm in length, more preferably at least
about 13 mm in length.
12. The smoking article of claim 1, wherein the transverse barrier
is concave relative to the direction of mainstream smoke drawn from
the rod of smokable material through the filter.
13. The smoking article of claim 1, wherein the smoking article has
a carbon monoxide to tar ratio of less than or equal to 1.
14. A flow restriction element for inclusion in a smoking article
of claim 1, the flow restriction element including: a first
integral tubular portion; a second integral tubular portion of
substantially the same external diameter as the first tubular
portion; a third central integral tubular portion located between
the first and second tubular portions the third tubular portion
being of reduced external diameter compared to the first and second
tubular portions; a transverse barrier having at least one orifice
provided therein, the transverse barrier being disposed between a
first cavity at least partially defined by an inner periphery of
the first tubular portion and a second cavity at least partially
defined by an inner periphery of the second tubular portion; and
one or more openings in a surface of the second or third tubular
portion in communication with the second cavity.
15. A filter for a smoking article including the flow restriction
element of claim 14.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority to European Application No.
09251336.5, filed May 18, 2009, the entire content of which is
incorporated herein by this reference thereto.
BACKGROUND
[0002] In a number of jurisdictions there are regulations
stipulating the maximum carbon monoxide, tar and nicotine yields
for cigarettes.
[0003] It is known to provide cigarettes and other smoking articles
with wrappers having a low permeability in order to reduce the
sidestream smoke generated during smoking thereof. However, while
advantageously reducing sidestream smoke, the inclusion of a low
permeability wrapper may disadvantageously increase the carbon
monoxide yields and hence carbon monoxide to tar ratios of the
mainstream smoke generated by such smoking articles.
[0004] While ventilation may be used to reduce the carbon monoxide
and tar deliveries, high levels of ventilation can
disadvantageously result in unacceptably low levels of resistance
to draw (RTD). Moreover, as ventilation reduces both gas phase and
particulate phase deliveries, it has little effect on carbon
monoxide to tar ratios.
[0005] The inclusion of, for example, one or more high density
cellulose acetate filter segments may be used to increase the
overall RTD of smoking articles with low permeability wrappers and
high levels of ventilation to an acceptable level. However, high
density cellulose acetate filter segments typically reduce tar
deliveries while having little or no effect on carbon monoxide
deliveries.
[0006] Therefore, it would be desirable to provide a smoking
article having a sidestream smoke reducing wrapper and a carbon
monoxide to tar ratio of less than or equal to 1.
SUMMARY
[0007] In a preferred embodiment, a smoking article includes a rod
of smokable material and a filter including a flow restriction
element attached to the rod of smokable material. Preferably, the
flow restriction element includes a first upstream integral tubular
portion, a second downstream integral tubular portion of
substantially the same external diameter as the first tubular
portion, a third central integral tubular portion located between
the first and second tubular portions, the third tubular portion
being of reduced external diameter compared to the first and second
tubular portions, and a transverse barrier having at least one
orifice provided therein. The transverse barrier is disposed
between a first upstream cavity at least partially defined by an
inner periphery of the first tubular portion and a second
downstream cavity at least partially defined by an inner periphery
of the second tubular portion. A ventilation zone in communication
with the second cavity is included at a location along the
filter.
[0008] In the preferred embodiment, the transverse barrier has a
single substantially central orifice having a diameter ranging from
about 0.4 mm to about 0.8 mm provided therein. Preferably, the
filter is attached to the rod of smokable material by a band of
tipping paper and the ventilation zone includes at least one
circumferential row of perforations provided through a portion of
the tipping paper overlying the third tubular portion of the flow
restriction element. Also preferably, the first cavity of the flow
restriction element is at least partially defined by an inner
periphery of the first and third tubular portions. Moreover, one or
more openings are provided in an upstream transverse end surface of
the second tubular portion that form a communication path between
the second cavity and the at least one circumferential row of
perforations. Also in the preferred embodiment, the second cavity
of the flow restriction element is at least partially defined by an
inner periphery of the second and third tubular portions.
Preferably, one or more openings are provided in a circumferential
surface of the third tubular portion that form a communication path
between the second cavity and the at least one circumferential row
of perforations. Also preferably, the filter further includes a
first filter segment upstream of the flow restriction element and a
second filter segment downstream of the flow restriction element.
Moreover, the wrapper has a basis weight ranging from about 35
g/m.sup.2 to about 60 g/m.sup.2, a filler loading ranging from
about 20 percent to about 50 percent by weight, a permeability
ranging from about 2 Coresta units to about 18 Coresta units, and
about 0.3 percent to about 5 percent by weight of a burn modifier.
Preferably, the smoking article has a ventilation level of at least
about 50 percent, preferably of at least about 60 percent. Also
preferably, the flow restriction element is at least about 10 mm in
length, more preferably at least about 13 mm in length. Moreover,
the transverse barrier is concave relative to the direction of
mainstream smoke drawn from the rod of smokable material through
the filter. In the preferred embodiment, the smoking article has a
carbon monoxide to tar ratio of less than or equal to 1.
[0009] In another embodiment, a flow restriction element includes a
first integral tubular portion, a second integral tubular portion
of substantially the same external diameter as the first tubular
portion, a third central integral tubular portion located between
the first and second tubular portions the third tubular portion
being of reduced external diameter compared to the first and second
tubular portions, a transverse barrier having at least one orifice
provided therein, the transverse barrier being disposed between a
first cavity at least partially defined by an inner periphery of
the first tubular portion and a second cavity at least partially
defined by an inner periphery of the second tubular portion, and
one or more openings in a surface of the second or third tubular
portion in communication with the second cavity.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The invention will be further described, by way of example
only, with reference to the accompanying drawings.
[0011] FIG. 1 is an expanded perspective view of a smoking article
according to a first embodiment of the invention with the tipping
paper and filter plug wrap partially unfolded to reveal the
internal components of the filter.
[0012] FIG. 2 is a partial longitudinal cross-sectional view of the
filter of the smoking article of FIG. 1.
[0013] FIG. 3 is a transverse cross-sectional view of the flow
restriction element of the filter of the smoking article of FIG. 2
along the line A-A (shown by a dotted line in FIG. 2).
[0014] FIG. 4 is a partial longitudinal cross-sectional view of the
filter of a smoking article according to a second embodiment of the
invention.
[0015] FIG. 5 is a transverse cross-sectional view of the flow
restriction element of the filter of the smoking article of FIG. 4
along the line B-B (shown by a dotted line in FIG. 3).
DETAILED DESCRIPTION
[0016] In a preferred embodiment, a smoking article includes a rod
of smokable material and a filter including a flow restriction
element attached to the rod of smokable material. Preferably, the
flow restriction element includes: a first upstream integral
tubular portion; a second downstream integral tubular portion of
substantially the same external diameter as the first tubular
portion; and a third central integral tubular portion located
between the first and second tubular portions, the third tubular
portion being of reduced external diameter compared to the first
and second tubular portions. A transverse barrier having at least
one orifice provided therein is disposed between a first upstream
cavity at least partially defined by an inner periphery of the
first tubular portion and a second downstream cavity at least
partially defined by an inner periphery of the second tubular
portion. A ventilation zone in communication with the second cavity
is provided at a location along the filter.
[0017] In another embodiment, a flow restriction element for
inclusion in a smoking article includes: a first integral tubular
portion; a second integral tubular portion of substantially the
same external diameter as the first tubular portion; a third
central integral tubular portion located between the first and
second tubular portions, the third tubular portion being of reduced
external diameter compared to the first and second tubular
portions; a transverse barrier having at least one orifice provided
therein disposed between a first cavity at least partially defined
by an inner periphery of the first tubular portion and a second
cavity at least partially defined by an inner periphery of the
second tubular portion; and one or more openings in a surface of
the second or third tubular portion in communication with the
second cavity.
[0018] In yet another embodiment, a filter for a smoking article
including a flow restriction element is provided.
[0019] Throughout the specification, the terms `upstream` and
`downstream` are used to describe the relative positions of
components of the smoking article of the invention in relation to
the direction of mainstream smoke drawn from the rod of smokable
material through the filter during smoking thereof.
[0020] The inclusion of a filter including a flow restriction
element and ventilation zone having the features specified above
advantageously enables the production of highly ventilated smoking
articles according to the invention with a desired RTD in which the
carbon monoxide to tar ratio of the mainstream smoke is maintained
to at an acceptable value. As described in more detail below, this
is the case even when the rod of smokable material of the smoking
article includes a sidestream smoke reducing wrapper.
[0021] Smoking articles according to the invention with filters
including a flow restriction element having the features specified
above may be advantageously produced using existing filter
combining and cigarette manufacturing equipment without the need
for significant modification. Due to its shape, the flow
restriction element is resilient and can be compressed during
manufacture of filters and smoking articles according to the
invention, in particular during the process of attaching filters
according to the invention to rods of smokable material in order to
produce smoking articles according to the invention. This
advantageously facilitates the manufacture of filters and smoking
articles according to the invention using existing filter combining
and cigarette manufacturing equipment.
[0022] The reduced external diameter of the third tubular portion
of the flow restriction element compared to the first and second
tubular portions thereof advantageously establishes a ventilation
zone between the periphery of the filter and the exterior of the
third tubular portion. At the same time, the increased external
diameter of the first and second tubular portions of the flow
restriction element compared to the third tubular portion
advantageously provide reinforcement so that the filter does not
collapse when, for example, the smoking article is held between a
consumer's fingers.
[0023] The first upstream cavity of the flow restriction element
advantageously allows mainstream smoke drawn through the rod of
smokable material in use to concentrate around the at least one
orifice in the transverse barrier before being drawn further
downstream through the at least one orifice. In addition, the first
upstream cavity helps to prevent blockage of the at least one
orifice during smoking.
[0024] The number of orifices provided in the transverse barrier
and the dimensions thereof may be selected in order to achieve a
desired RTD and carbon monoxide to tar ratio. Preferably, the
transverse barrier includes a single orifice, more preferably a
substantially central single orifice. Where the transverse barrier
includes a single substantially central orifice, the orifice is
preferably between about 0.4 mm and about 0.8 mm in diameter, more
preferably about 0.6 mm in diameter.
[0025] Preferably, the at least one orifice is between about 0.2 mm
and about 1 mm in length, more preferably about 0.7 mm in length.
Throughout the specification, the term `length` is used to denote
the dimension in the longitudinal direction of the smoking article.
The length of the at least one orifice is equal to the thickness of
the transverse barrier.
[0026] Preferably the at least one orifice is sized to contribute
sufficient pressure drop such that the smoking article has a RTD of
between about 30 mm WG (water gauge) and about 120 mm WG, more
preferably of at least about 40 mm WG.
[0027] The smoke impermeable transverse barrier may be of any
suitable shape. For example, the transverse barrier may be
substantially perpendicular to the longitudinal axis of the smoking
article. Alternatively, the transverse barrier may be
frustroconical and convergent or divergent relative to the
direction of mainstream smoke drawn from the rod of smokable
material through the filter. In yet further embodiments, the
transverse barrier may be concave or convex relative to the
direction of mainstream smoke drawn from the rod of smokable
material through the filter. Preferably, the transverse barrier is
concave relative to the direction of mainstream smoke drawn from
the rod of smokable material through the filter. This
advantageously eases compression of the flow restriction element
during manufacture of filters and smoking articles according to the
invention, in particular during the process of attaching filters
according to the invention to rods of smokable material in order to
produce smoking articles according to the invention.
[0028] The second downstream cavity of the flow restriction element
advantageously allows mainstream smoke drawn through the one or
more orifices provided in the transverse barrier to mix with air
drawn through the ventilation zone prior to being drawn into a
consumer's mouth.
[0029] The ventilation zone provides ventilation of mainstream
smoke drawn from the rod of smokable material in the second cavity
of the flow restriction element of the filter, that is at a
location downstream of the at least one orifice in the transverse
barrier of the flow restriction element. Preferably, no ventilation
is provided upstream of the at least one orifice in the transverse
barrier. Provision of ventilation only downstream of the at least
one orifice advantageously limits the extent to which a consumer
may attempt to draw harder on the smoking article during a puff. As
the flow rate of a puff increases, pressure drop at the flow
restriction element increases more rapidly compared to in a smoking
article including a conventional cellulose acetate tow filter. Thus
a consumer drawing harder during a puff results in increased
ventilation of the mainstream smoke rather than increased
mainstream smoke delivery. Furthermore, provision of ventilation
only downstream of the at least one orifice in the transverse wall
of the flow restriction element advantageously separates the
functions of the ventilation zone and at least one orifice
(ventilation levels and RTD, respectively).
[0030] Preferably, the filter is attached to the rod of smokable
material by a band of substantially air impermeable tipping paper.
Preferably, the ventilation zone includes at least one
circumferential row of perforations provided through a portion of
the tipping paper, more preferably at least one circumferential row
of perforations provided through a portion of the tipping paper
overlying the third tubular portion of the flow restriction
element.
[0031] Preferably, the at least one circumferential row of
perforations is located at least 12 mm from the mouth end of the
smoking article.
[0032] The perforations in the tipping paper may be made prior to
or during construction of the smoking article using conventional
techniques. For example, the perforations in the tipping paper may
be created using online laser perforation, mechanical perforation
or electrostatic perforation. Preferably, the tipping paper is
pre-perforated.
[0033] In the preferred embodiment, the first cavity of the flow
restriction element is at least partially defined by an inner
periphery of the first and third tubular portions of the flow
restriction element and the second cavity of the flow restriction
element is at least partially defined by an inner periphery of the
second tubular portion of the flow restriction element.
[0034] In this embodiment, one or more openings are preferably
provided in an upstream transverse end surface of the second
tubular portion that form a communication path between the second
cavity and the at least one circumferential row of perforations of
the ventilation zone. More preferably, a plurality of substantially
equally circumferentially spaced apart openings are provided in an
upstream transverse end surface of the second tubular portion that
form a communication path between the second cavity and the at
least one circumferential row of perforations of the ventilation
zone. For example, twelve substantially equally circumferentially
spaced apart openings may be provided in the upstream transverse
end surface of the second tubular portion that extends radially
outward from the third tubular portion.
[0035] Preferably, the one or more openings have a diameter ranging
from about 0.3 mm to about 0.8 mm, more preferably of about 0.5
mm.
[0036] In an alternative embodiment, the first cavity of the flow
restriction element is at least partially defined by an inner
periphery of the first tubular portion of the flow restriction
element and the second cavity of the flow restriction element is at
least partially defined by an inner periphery of the second and
third tubular portions of the flow restriction element.
[0037] In this embodiment, one or more openings are preferably
provided in a circumferential surface of the third tubular portion
that form a communication path between the second cavity and the at
least one circumferential row of perforations of the ventilation
zone.
[0038] For example, a pair of elongate opposed openings may be
provided in the upstream circumferential surface of the third
tubular portion.
[0039] Preferably, smoking articles according to the invention have
a ventilation level ranging from about 50 percent to about 90
percent, more preferably ranging from about 60 percent to about 80
percent, most preferably of about 70 percent.
[0040] The flow restriction element may be made from any suitable
materials or combination or materials. Suitable materials from
which the flow restriction element may be formed include, but not
limited to, plastic (for example, polypropylene, polyethylene,
polystyrene, nylon, polysulfone, polyester and polyurethane),
cellulosic material and combinations or composites thereof.
[0041] Preferably, the flow restriction element is made from a
biodegradable material, more preferably from a biodegradable
polymeric material. Suitable biodegradable polymeric materials are
known in the art and commercially available under the brand name
Mater-Bi.RTM. from Novamont of Novara, Italy and under the brand
names Ecoflex.RTM. and Ecovio.RTM. from BASF of Ludwigshafen,
Germany.
[0042] Preferably, the flow restriction element is a single piece,
more preferably a single injection molded piece.
[0043] Preferably, the flow restriction element ranges from about
10 mm to about 20 mm in length, more preferably from about 12 mm to
about 14 mm in length, most preferably about 13 mm in length.
[0044] Preferably, the first tubular portion of the flow
restriction element is at least about 4 mm in length, more
preferably at least about 5 mm in length.
[0045] Preferably, the second tubular portion of the flow
restriction element is at least about 3 mm in length, most
preferably about 3.5 mm in length.
[0046] Preferably, the third tubular portion of the flow
restriction element is at least about 3 mm in length, most
preferably about 3.5 mm in length.
[0047] Preferably, the transverse barrier is at least about 1 mm,
more preferably at least about 1.5 mm from the downstream end of
the second tubular portion of the flow restriction element.
[0048] Preferably, the external diameter of the first and second
tubular portions of the flow restriction element ranges from about
6 mm to about 9 mm, more preferably ranges from about 7 mm to about
8.4 mm, most preferably from about 7.5 mm to about 7.9 mm.
[0049] Preferably, the external diameter of the third tubular
portion of the flow restriction element ranging from about 4 mm to
about 7.5 mm, more preferably from about 4.5 mm to about 6.8 mm,
most preferably from about 4.5 mm to about 5.5 mm.
[0050] The filter may further include one or more filter segments
upstream of the flow restriction element. Alternatively, or in
addition, the filter may further include one or more filter
segments downstream of the flow restriction element. In a preferred
embodiment, the filter further includes a first filter segment
upstream of the flow restriction element and a second filter
segment downstream of the flow restriction element. Preferably, the
first and second filter segments are between about 5 mm and about
12 mm in length, more preferably between about 6 mm and about 8 mm
in length, most preferably about 7 mm in length.
[0051] Where the filter includes one or more filter segments
upstream of the flow restriction element and one or more filter
segments downstream of the flow restriction element, the upstream
and downstream filter segments may be the same or different. For
example, the filter may include a pair of identical segments of
cellulose acetate tow disposed on either side of the flow
restriction element. Alternatively, the filter may include a plug
of cellulose acetate tow upstream of the flow restriction element
and a hollow tube of for example, paper, cardboard or cellulose
acetate downstream of the flow restriction element.
[0052] Preferably, the one or more filter segments include
filtration material of low particulate phase filtration efficiency.
Preferably, the particulate phase filtration efficiency of each of
the one or more filter segments is less than about 30 percent, more
preferably less than about 20 percent. In a particularly preferred
embodiment, the filter includes a first filter segment of low
particulate phase filtration efficiency upstream of the flow
restriction element and a second filter segment of low particulate
phase filtration efficiency downstream of the flow restriction
element.
[0053] The one or more filter segments may include cellulosic
material, such as cellulose acetate tow, or other suitable fibrous
filtration material of low filtration efficiency. Where the one or
more filter segments include cellulose acetate tow, the denier per
filament and total denier of the tow may be selected in order to
achieve a desired particulate phase efficiency and RTD. Preferably,
the cellulose acetate tow has a denier per filament of about 8 or
greater and a total denier of about 28,000 or less.
[0054] Preferably, the flow restriction element and, where present,
one or more filter segments are circumscribed by a band of plug
wrap. In one embodiment, the flow restriction element and one or
more filter segments are circumscribed by a band of substantially
air impermeable plug wrap, preferably a band of plug wrap having a
permeability of between about 7,000 Coresta units and about 20,000
Coresta units. In an alternative embodiment, the flow restriction
element and one or more filter segments are circumscribed by a band
of substantially air permeable plug wrap.
[0055] Preferably, the band of plug wrap is affixed to the
circumferential outer surface of the first tubular portion of the
flow restriction element. More preferably, the plug wrap is affixed
to the circumferential outer surface of the first tubular portion
of the flow restriction element so as to establish a substantially
air-tight seal at the outer surface of the first tubular portion.
Most preferably, the band of plug wrap is affixed to the
circumferential outer surfaces of the first and second tubular
portions of the flow restriction element.
[0056] Where the filter includes a filter segment upstream of the
flow restriction element, the band of plug wrap is preferably
affixed to the circumferential outer surface of the upstream filter
segment. More preferably, the plug wrap is affixed to the
circumferential outer surfaces of the upstream filter segment and
the first tubular portion of the flow restriction element so as to
establish a substantially air-tight seal at the outer surface of
the first tubular portion of the flow restriction element.
[0057] Where the filter includes a filter segment downstream of the
flow restriction element, the band of plug wrap is preferably
affixed to the circumferential outer surface of the downstream
filter segment.
[0058] The band of plug wrap may be affixed to the flow restriction
element and one or more filter segments using, for example, an
adhesive. An air-tight seal between the band of plug wrap and the
first tubular portion of the flow restrictor may be obtained
through the use of an adhesive offering a good cohesion and a high
surface tackiness. Suitable adhesives are known in the art and
commercially available under the brand name Adhesin from Henkel of
Dusseldorf, Germany.
[0059] As stated above, the filter including the band of plug wrap
is preferably attached to the rod of smokable material by a band of
substantially air impermeable tipping paper.
[0060] Where the filter includes a band of substantially air
impermeable plug wrap, the ventilation zone preferably includes at
least one circumferential row of perforations provided through a
portion of the tipping paper and the plug wrap that are formed
online during manufacture of the smoking article.
[0061] Where the filter includes a band of substantially air
permeable plug wrap, the filter is preferably attached to the rod
of smokable material by a band of pre-perforated tipping paper
including at least one circumferential row of perforations.
[0062] The RTD of smoking articles according to the invention may
be adjusted by use of pre-perforated tipping paper and air
permeable plug wrap. The at least one orifice of the flow
restriction element may be sized to allow substantially all of the
ventilating air that, in use, flows through the perforations in the
tipping paper and air permeable plug wrap to flow into the second
downstream cavity. In addition, by providing the perforations in a
portion of the tipping paper overlying the third tubular portion of
the flow restriction element, and hence ventilation zone, and
separating the ventilation zone from the second downstream cavity,
where mainstream smoke drawn from the rod of smokable material
mixes with the ventilating air, the mainstream smoke does not flow
upstream and exit through the perforations in the tipping paper.
The levels of ventilation of smoking articles according to the
invention may thus be advantageously varied through the use of
different pre-perforated tipping papers or plug wraps with
different porosity levels or combinations thereof.
[0063] Preferably, the filter has an overall length ranging from
about 20 mm to about 34 mm, more preferably from about 25 mm to
about 30 mm, most preferably about 27 mm.
[0064] Preferably, the filters of smoking articles according to the
invention have an overall encapsulated RTD ranging from about 250
mm WG to about 350 mm WG, more preferably of between about 275 mm
WG and 325 mm WG.
[0065] Preferably, smoking articles according to the invention have
an unencapsulated RTD of at least about 30 mm WG, more preferably
of at least about 40 mm WG.
[0066] Preferably, the rod of smokable material includes tobacco
circumscribed by a wrapper, more preferably tobacco cut filler
circumscribed by a wrapper.
[0067] Preferably, the rod of smokable material includes a wrapper
that results in the production of reduced amounts of sidestream
smoke. Suitable sidestream smoke reducing wrappers for use in
smoking articles according to the invention, and methods for
producing such wrappers, are well known in the art and described
in, for example, U.S. Pat. No. 5,152,304.
[0068] Preferably, the wrapper has a high basis weight and a low
permeability. More preferably, the wrapper is of the type described
in U.S. Pat. No. 5,152,304.
[0069] Preferably, the wrapper has a basis weight of at least about
35 g/m.sup.2, more preferably a basis weight of between about 35
g/m.sup.2 and about 60 g/m.sup.2, most preferably a basis weight of
between about 40 g/m.sup.2 and about 50 g/m.sup.2.
[0070] Preferably, the wrapper has a permeability of about 18
Coresta units or less, more preferably ranging from about 4 Coresta
units to about 18 Coresta units, most preferably ranging from about
5 Coresta units to about 8 Coresta units.
[0071] Preferably, the wrapper includes a filler, more preferably
an inorganic filler, most preferably calcium carbonate. Preferably,
the wrapper has a filler loading of between about 20 percent and
about 50 percent by weight, more preferably of about 40 percent by
weight.
[0072] Preferably, the wrapper further includes a burn modifier.
More preferably, the wrapper includes between 0.3 percent and 5
percent by weight of a burn modifier. Suitable burn modifiers are
known in the art and include, but are not limited to, acidic salts
of inorganic or organic acids, including monobasic potassium and
sodium salts of polyvalent inorganic acids (such as phosphoric,
pyrophosphoric, boric, and sulfuric acids) and mono-potassium and
sodium salts of carboxylic acids (such as citric, succinic, and
fumaric acids), compounds that thermally decompose to generate
acidic species in situ, including salts of polyvalent acids with at
least one labile proton, various esters that are acidic precursors,
including phosphate esters (such as the potassium salt of
.alpha.-D-glucose-1-phosphate), and combinations thereof.
Preferably, the burn modifier is an acidic salt, more preferably
monobasic potassium phosphate.
[0073] Preferably, smoking articles according to the invention have
a carbon monoxide to tar ratio of less than or equal to 1.
[0074] Preferably, smoking articles according to the invention have
a total nicotine free dry particulate matter (NFDPM) or `tar`
delivery ranging from about 3 mg to about 12 mg.
[0075] The smoking article 10 according to the first embodiment of
the invention shown in FIG. 1 includes a cylindrical tobacco rod 12
and a filter 14. The filter 14 is attached to the tobacco rod 12 by
a band of tipping paper 16, which circumscribes the filter 14 and
an adjacent portion of the tobacco rod 12, which includes a charge
of smokable material such as tobacco cut filler 18 circumscribed
preferably by a high basis weight, low permeability, paper wrapper
20.
[0076] The filter 14 includes a first filter segment 22 adjacent to
and abutting the tobacco rod 12, a second filter segment 24 at the
mouth end of the smoking article 10 and a one-piece, injection
molded, flow restriction element 26 disposed between the first
filter segment 22 and the second filter segment 24. The first and
second filter segments 22, 24 are preferably low particulate
efficiency cellulose acetate tow filter segments.
[0077] The first and second filter elements 22, 24 and the flow
restriction element 26 are circumscribed by a band of plug wrap
28.
[0078] As shown in more detail in FIG. 2, the flow restriction
element 26, which is preferably formed of biodegradable polymeric
material, includes a first upstream integral tubular portion 30
adjacent to and abutting the first filter segment 22, a second
downstream integral tubular portion 32 of substantially the same
external diameter as the first tubular portion 30, which is
adjacent to and abuts the second filter segment 24, and a third
central integral tubular portion 34 located between and of reduced
external diameter compared to the first and second tubular portions
30, 32. The plug wrap 28 is affixed to the circumferential outer
surfaces of the first filter element 22 and the first tubular
portion 30 of the flow restriction element 26 by an adhesive (not
shown) so as to form a substantially air-tight connection or joint
at the outer surface of the first tubular portion 30 of the flow
restriction element 26.
[0079] Due to the reduced external diameter of the third tubular
portion 34 compared to the first and second tubular portions 30,
the inner surface of the plug wrap 28 is spaced apart from the
circumferential outer surface of the third tubular portion 34 as
shown in FIG. 2. As described further below, the space between the
plug wrap 28 and overlying band of tipping paper 16 and the
circumferential outer surface of the third tubular portion 34 forms
a ventilation zone.
[0080] The flow restriction element 26 further includes a
transverse barrier 36 with a single central orifice 38 of reduced
diameter provided therein. As shown in FIG. 2, the transverse
barrier 36 is disposed between a first upstream cavity 40, which is
at least partially defined by the inner peripheries of the first
and third tubular portions 30, 34 of the flow restriction element
26, and a second downstream cavity 42, which is at least partially
defined by the inner periphery of the second tubular portion 32 of
the flow restriction element.
[0081] One or more circumferential rows of perforations 44 (shown
by dashed lines in FIGS. 1 and 2) are provided through a portion of
the tipping paper 16 and plug wrap 28 overlying the third tubular
portion 34 of the flow restriction element 26. As shown in FIG. 3,
a plurality of substantially equally circumferentially spaced apart
openings 46 are provided in the upstream transverse end surface of
the second tubular portion 32 that extends radially outward around
the third tubular portion 34. These openings 46 form a
communication path between the one or more circumferential rows of
perforations 44 provided in the tipping paper 16 and plug wrap 28
and the second cavity 42, as shown in FIG. 2.
[0082] In use, mainstream smoke from the tobacco rod 12 of the
smoking article 10 is drawn downstream through the first filter
segment 22 of the filter 14 into the first cavity 40 of the flow
restriction element 26. Mainstream smoke drawn into the first
cavity 40 concentrates around the central orifice 38 of the
transverse barrier 36 of the flow restriction element 26 before
being drawn further downstream through the central orifice 38 into
the second cavity 42 of the flow restriction element 26.
[0083] Ventilating air is also drawn into the second cavity 42
through the one or more circumferential rows of perforations 44 in
the tipping paper 16 and plug wrap 28 and the plurality of
substantially equally circumferentially spaced apart openings 46
provided in the upstream transverse end surface of the second
tubular portion 32. Mainstream smoke drawn through the central
orifice 38 in the transverse barrier 36 mixes with the ventilating
air in the second cavity 42 before being drawn further downstream
through the second filter element 24.
[0084] During smoking, the high basis weight, low permeability
paper wrapper 20 of the tobacco rod 12 advantageously reduces the
sidestream smoke generated by the smoking article 10 in a known
manner.
[0085] The smoking article according to the second embodiment of
the invention shown in FIGS. 4 and 5 is of largely similar
construction and design as the smoking article 10 according to the
first embodiment of the invention shown in FIGS. 1 to 3. The
similar reference numerals are used in FIGS. 4 and 5 for features
of the smoking article according to the second embodiment of the
invention that correspond to features of the smoking article
according to the first embodiment of the invention previously
described.
[0086] The principal differences between the smoking article 10
according to the first embodiment of the invention shown in FIGS. 1
to 3 and the smoking article according to the second embodiment of
the invention shown in FIGS. 4 and 5 are the locations of the
openings that form a communication path between the one or more
circumferential rows of perforations in the tipping paper and plug
wrap and the second cavity, and the location of the transverse
barrier in the flow restriction element.
[0087] As shown in FIG. 4 in the flow restriction element 26' of
the filter 14 of the smoking article according to the second
embodiment of the invention, the transverse barrier 36' is disposed
between a first upstream cavity 40', which is at least partially
defined by the inner periphery of the first tubular portion 30' of
the flow restriction element 26, and a second downstream cavity
42', which is at least partially defined by the inner peripheries
of the second and third tubular portions 32', 34' of the flow
restriction element 26'.
[0088] In the second embodiment, a pair of opposed elongate
openings 46', which form a communication path between the one or
more circumferential rows of perforations 44 in the tipping paper
16 and plug wrap 28 and the second cavity 42', are provided in the
circumferential surface of the third tubular body portion 34' of
the flow restriction element 26' as shown in FIG. 5.
[0089] In use, ventilating air is drawn into the second cavity 42'
through the one or more circumferential rows of perforations 44 in
the tipping paper 16 and plug wrap 28 and the pair of opposed
elongate openings 46' provided in the circumferential surface of
the third tubular body portion 34', where it mixes with mainstream
smoke drawn through the central orifice 38' in the transverse
barrier 36'.
[0090] The tobacco rods 12 of the smoking articles according to the
first and second embodiments of the invention may be constructed
using conventional cigarette rod making equipment wherein the
tobacco cut filler 18 is air formed into a continuous rod on a
travelling belt and enwrapped with a continuous ribbon of the high
basis weight, low permeability, paper wrapper 20, which is then
glued along its longitudinal seam.
[0091] The filters 14 of the smoking articles according to the
first and second embodiments of the invention may also be
constructed using existing high speed filter rod making equipment
employing known combining techniques.
[0092] The filters 14 and the tobacco rods 12 may then be combined
and attached to one another by affixing the band of tipping paper
16 around the filter 14 and an adjacent portion of the tobacco rod
12 using existing machinery employed for attaching filters to
tobacco rods during the production of known filter cigarettes.
[0093] Table 1 provides the puff count, total amounts of smoke
nicotine (SN), tar and carbon monoxide (CO) and CO/tar and CO/SN
ratios for: a first cigarette (Cigarette A) constructed in
accordance with the first embodiment of the invention shown in
FIGS. 1 to 3 in which the first and second filter segments are
plugs of low particulate efficiency cellulose acetate tow; a second
cigarette (Cigarette B) according to the invention of largely
identical construction to Cigarette A, but in which the second
filter segment is replaced by a hollow cylindrical tube of
cellulose acetate tow; and a third cigarette (Cigarette C)
according to the invention of largely identical construction to
Cigarette A, but in which the high basis weight, low permeability
wrapper of the tobacco rod is replaced by a paper wrapper of
conventional basis weight and permeability.
[0094] For comparison, Table 1 also provides the puff count, total
amounts of smoke nicotine (SN), tar and carbon monoxide (CO) and
CO/tar and CO/SN ratios for three cigarettes not in accordance with
the invention having conventional cellulose acetate tow filters.
Two of the cigarettes have tobacco rods with high basis weight, low
permeability wrappers (Cigarettes D and E), and one of the
cigarettes has a tobacco with a wrapper of conventional basis
weight and permeability (Cigarette F).
[0095] As shown in Table 1, for the cigarettes having conventional
cellulose acetate tow filters inclusion of a high basis weight, low
permeability wrapper (Cigarettes D and E) leads to an increase
carbon monoxide yield. Furthermore, while increasing the
ventilation level of the cigarettes having conventional cellulose
acetate tow filters and a high basis weight, low permeability
wrapper (cigarettes D and E) significantly reduces the carbon
monoxide yield, it does not significantly affect the carbon
monoxide to tar ratio.
[0096] In contrast to the cigarettes having conventional cellulose
acetate tow filters, the cigarettes according to the invention
(Cigarettes A, B and C) all have carbon monoxide to tar ratios of
less than 1.0. In particular, as shown in Table 1, the puff count
and smoke nicotine (SN) and tar yields of the cigarette according
to the invention having a high basis weight, low permeability
wrapper and a second filter segment consisting of a hollow
cylindrical tube of cellulose acetate tow (Cigarette B) are very
similar to those of the cigarette having a conventional cellulose
acetate tow filter and a wrapper of conventional basis weight and
permeability (Cigarette F). However, despite the inclusion of a
side stream smoke reducing wrapper, the carbon monoxide yield and
carbon monoxide to tar and carbon monoxide to smoke nicotine ratios
of Cigarette B are advantageously significantly reduced compared to
Cigarette F.
TABLE-US-00001 TABLE 1 Cigarette A B C D E F Tobacco rod Length
(mm) 57 57 57 57 57 57 Basis weight of wrapper 45 45 25 45 45 25
(g/m.sup.2) Permeability of wrapper 6 6 56 6 6 56 (Coresta Unit)
Filter Overall length (mm) 27 27 27 27 27 27 Resistance to draw (mm
WG) 298 298 298 65 67 108 Ventilation (percent) 71 70 70 53 39 46
Length of first filter segment 7 7 7 27 27 27 Length of flow
restriction 13 13 13 -- -- -- element Length of second filter 7 7 7
-- -- -- segment Denier per filament of the 8Y 8Y 8Y 5.5Y 5.5Y 2.5Y
cellulose acetate tow of the or each filter segment Total denier of
the cellulose 28,000 28.000 28,000 35,000 35,000 37,000 acetate tow
of the or each filter segment Length of flow restriction 13 13 13
-- -- -- element Cigarette Resistance to draw (mm WG) 42 33 44 71
82 109 SN (mg/cigarette) 0.49 0.58 0.49 0.63 0.76 0.56 Tar
(mg/cigarette) 5.09 5.90 4.46 7.00 8.90 5.98 CO (mg/cigarette) 4.12
4.03 2.95 9.30 12.80 7.03 Puff count (number/cigarette) 7.60 7.33
6.95 7.60 7.00 7.50 CO/Tar 0.8 0.7 0.7 1.3 1.4 1.2 CO/SN 8.4 6.9
6.0 14.8 16.8 12.6
[0097] The invention has been exemplified above with respect to
smoking articles including filters having first and second filter
segments including plugs of cellulose acetate tow. However, it will
be appreciated that smoking articles according to the invention may
include filters having one or more filter segments including other
materials such as paper (for example, filter paper or carbon
paper), cardboard, plastic (for example, polypropylene,
polyethylene, polystyrene, nylon, polysulfone, polyester or
polyurethane), biopolymers and combinations thereof.
[0098] Furthermore, while the invention has been exemplified above
with respect to smoking articles including filters having flow
restriction elements including transverse barriers with a single
substantially central orifice provided therein, it will be
appreciated that smoking articles according to the invention may
include filters including transverse barriers with a single
non-central orifice or two or more orifices provided therein.
[0099] In this specification, the word "about" is often used in
connection with numerical values to indicate that mathematical
precision of such values is not intended. Accordingly, it is
intended that where "about" is used with a numerical value, a
tolerance of .+-.10% is contemplated for that numerical value.
[0100] In this specification the words "generally" and
"substantially" are sometimes used with respect to terms. When used
with geometric terms, the words "generally" and "substantially" are
intended to encompass not only features which meet the strict
definitions but also features which fairly approximate the strict
definitions.
[0101] While the foregoing describes in detail a preferred smoking
article including a filter having a flow restriction element with
reference to a specific embodiments thereof, it will be apparent to
one skilled in the art that various changes and modifications may
be made to the smoking article, which do not materially depart from
the spirit and scope of the foregoing description. Accordingly, all
such changes, modifications, and equivalents that fall within the
spirit and scope of the appended claims are intended to be
encompassed thereby.
* * * * *