U.S. patent number 3,791,265 [Application Number 05/217,797] was granted by the patent office on 1974-02-12 for apparatus for making tobacco smoke filter.
This patent grant is currently assigned to Imperical Tobacco Group Limited. Invention is credited to David Thomas Westcott, Geoffrey Roger Woodman.
United States Patent |
3,791,265 |
Westcott , et al. |
February 12, 1974 |
APPARATUS FOR MAKING TOBACCO SMOKE FILTER
Abstract
A tobacco smoke filter is in the form of a cylinder having a low
resistance core and a high resistance end wall which cause smoke
flow radially through the cylinder wall. The filter is preferably
made by compacting the central core of a filter plug to form the
dense end wall. Such filter plugs have an efficiency of two or
three times that of a conventional filter of the same pressure
drop.
Inventors: |
Westcott; David Thomas
(Bristol, EN), Woodman; Geoffrey Roger (Bristol,
EN) |
Assignee: |
Imperical Tobacco Group Limited
(London, EN)
|
Family
ID: |
9760458 |
Appl.
No.: |
05/217,797 |
Filed: |
January 14, 1972 |
Foreign Application Priority Data
|
|
|
|
|
Feb 1, 1971 [GB] |
|
|
3,550/71 |
|
Current U.S.
Class: |
493/42; 131/339;
493/47 |
Current CPC
Class: |
A24D
3/0283 (20130101) |
Current International
Class: |
A24D
3/02 (20060101); A24D 3/00 (20060101); B31f
001/00 () |
Field of
Search: |
;93/1C,77FT,1WZ |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Juhasz; Andrew R.
Assistant Examiner: Coan; James F.
Attorney, Agent or Firm: Larson, Taylor & Hinds
Claims
What we claim is:
1. Apparatus for making a selectively compacted tobacco smoke
filter comprising a fluted drum for holding filter plug blanks
thereon, a compacting rod alignable with each flute and means for
reciprocating the rod relative to each flute, the rod having a
diameter which is smaller than that of a tobacco smoke filter held
in a flute of the drum whereby the rod is adapted to compact only a
core section of the filter, leaving an annular uncompacted wall
extending around the compacted core section.
2. Apparatus as claimed in claim 1 comprising two coaxial
compacting rods for each flute disposed at opposite ends of the
flute, and means for reciprocating the rods simultaneously relative
to each flute to compact two core sections of a double tobacco
smoke filter held in a flute of the drum.
Description
This invention concerns a filter for tobacco smoke, cigarettes made
therewith and a process and apparatus for making such filters. The
term "cigarette" where used throughout this specification is
intended to include within its scope not only conventional
cigarettes but also cigars, cigarlettes and cigarillos.
According to one aspect of the present invention there is provided
a method of making a tobacco smoke filter for a cigarette
comprising providing a cylinder of filter material and compacting a
core section of the cylinder to provide an end wall which is denser
than the cylindrical wall of the filter.
Preferably the method comprises providing a double length filter
rod, compacting a core section of the rod from both ends
simultaneously to provide a central plug section denser than that
of the cylindrical wall and separating the rod transversely at the
central plug section to provide two hollow cylindrical filters each
with one denser end wall.
According to another aspect of the present invention, there is
provided apparatus for forming a filter plug having a compacted
core section comprising a fluted drum for holding filter plug
blanks thereon, a compacting rod aligned with each flute and
adapted to reciprocate relative to the flute, and means for
reciprocating each rod relative to each flute during rotation of
the drum to compact a core section of a filter plug blank held in a
flute of the drum.
According to another aspect of the present invention there is
provided a tobacco smoke filter for a cigarette comprising a
cylinder of filter material the interior of which provides a flow
path of lower resistance to flow than the wall of the cylinder, one
end of the cylinder being sealed with a tranverse wall member which
presents a higher resistance to flow than the wall of the cylinder,
whereby, in use, flow of smoke purely axially of the filter will be
inhibited, causing smoke flow through the cylinder wall.
The invention also includes a cigarette comprising a tobacco rod
and a hollow cylindrical filter having at the mouth end an end wall
of material denser than the cylindrical wall of the filter, and
smoke channels between the external surface of the filter and
wrapper, whereby in use tobacco smoke passing into the interior of
the filter from the tobacco rod will pass through the cylinder wall
and through the smoke channels to the mouth end of the
cigarette.
The invention is illustrated merely by way of example in the
accompanying drawings in which:
FIG. 1 is a longitudinal cross-section through a conventional
filter plug,
FIG. 2 is a longitudinal cross-section through a filter plug
according to the present invention,
FIGS. 3 and 4 illustrate one method providing a filter plug as
shown in FIG. 2,
FIGS. 5 and 6 illustrate a further method of providing the filter
plug of FIG. 2,
FIG. 7 illustrates an alternative way of effecting the method
illustrated by FIGS. 5 and 6,
FIG. 8 is a part sectional elevation of one form of apparatus for
making filter plugs according to the method described with
reference to FIG. 7,
FIG. 9 is a cross-section on line IX--IX of the apparatus shown in
FIG. 8,
FIGS. 10a and 10b are an end cross section and a lateral
cross-section respectively through a cigarette including a filter
according to the present invention.
FIG. 11a and 11b are an end cross-section and a lateral
cross-section respectively through a further cigarette
incorporating a filter according to the present invention, and
FIGS. 12a and 12b are an end cross-section and a lateral
cross-section respectively through yet a further cigarette
incorporating a filter according to the present invention.
Referring to the drawings, and in particular FIGS. 1 and 2, there
is shown in FIG. 1 a conventional filter plug 2 of cylindrical form
and made of cellulose acetate fibre. In a typical plug the
dimension a, which is the length of the cylindrical plug adapted to
be disposed longitudinally of the cigarette rod is 15 mm and
dimension b which is the diameter of the cylindrical plug, is 8 mm.
With the filter plug, tobacco smoke passes from one end face of the
cylinder to the other end face thereof longitudinally of the
cylindrical plug, as illustrated by arrows p. The pressure drop of
a typical cellulose acetate filter plug of these dimensions is 21/2
cm of water and the efficiency of a typical plug is 30 percent i.e.
30 percent of all particulate matter carried by the smoke passing
through such a plug is retained within the filter plug.
Referring now to FIG. 2 there is shown a cellulose acetate filter
plug 3 according to the present invention comprising a hollow
cylindrical member 4 sealed at one end with an end plug which is
denser than the wall 4 and which blanks off one end of the hollow
core. For comparison purposes, this plug is of the same overall
dimensions as plug 2 where a is 15 mm., b is 8 mm., and furthermore
c is 4 mm, d is 2 mm. and e is 4 mm. Because the density of the
plug 5 is greater than the density of the hollow cylindrical wall 4
the flow path adopted by the tobacco smoke passing through this
filter will be transversely of the cylindrical wall 4 as indicated
by arrows q . The smoke will not pass through the end plug 15 in
passing through the filter but will take the path of least
resistance.
With a filter plug of the type shown in FIG. 2, a typical pressure
drop has been found to be 1.8 cm. of water with an efficiency of 35
percent. Thus compared with the conventional plug shown in FIG. 1 a
substantially lower pressure drop is experienced whilst an increase
in efficiency is achieved.
The reason for these beneficial results is thought to be the
increased transverse area of filter plug material presented to the
path of the tobacco smoke. Thus the area of material presented to
the tobacco smoke in the plug 2 of FIG. 1 is that of a disc of
diameter b (16 .pi. sq.mm.) whereas in FIG. 2 the area presented to
the tobacco smoke is that of the surface of a cylinder of diameter
c and length a - e. (44 .pi. sq.mm.). The substantial increase in
cross-sectional area of filter material presented to the tobacco
smoke (a factor of 2.75) accounts for the beneficial results
achieved by decrease in pressure drop across the filter and/or
increase in efficiency.
FIGS. 3 and 4 illustrate one way of forming a filter plug according
to the present invention. In FIG. 3 a cylindrical plug 10 of
cellulose acetate length 15 mm. diameter 8 mm., is supported upon a
solid surface 6. A cutting tool 11 of diameter somewhat less than 4
mm. is plunged into the cylindrical rod for a distance of 11 mm.
whereby a core of the cellulose acetate is cut from the cylinder
and, as it is cut it is compacted or compressed by the tool 11 to
form a very dense wall 13 at the lower end of the cylinder as shown
in FIG. 4. If tearing is experienced in the cutting action, the use
of a warm tool can assist in providing a clean cut.
The resulting plug 12 is in the form of a hollow cylinder having a
cylindrical wall 14 of cellulose acetate having the same density as
that of the filter plug 10 from which it was formed, and an
integral end wall or plug 13 of a density which is greater than
that of the wall 14. The core 15 of the filter plug is hollow. By
forming the integral wall or end plug 13 denser than the wall 14
and since and wall 13 is sealed to the cylindrical wall 14 and
inhibits leaks, smoke is forced radially through the wall 14 of the
cylinder in passing through the filter.
Referring to FIGS. 5 and 6 there is illustated a further method of
providing a filter plug as shown in FIG. 2. In this embodiment a
cylindrical cellulose acetate blank 20 being 15 mm long and 8 mm
diameter and from which the filter plug is to be formed includes an
external cylindrical rod 21 of cellulose acetate packed at a
density similar to that of the plug 10 of FIG. 3 (i.e. at the
density required for the wall of the final cigarette filter).
Within the cylindrical rod 21 is a core 22 of 4 mm diameter made
from cellulose acetate of a density less than that of the wall 21
and thus more easily compressible. Such a blank may be conveniently
formed by co-extruding the core 22 of less dense cellulose acetate
with the surrounding cylindrical rod 21 of more dense cellulose
acetate.
To form a filter plug such as that shown in FIG. 2 the blank 20 of
FIG. 5 is placed upon a solid support 19. A piston 23 as shown in
FIG. 6 and of diameter somewhat less than 4 mm is plunged through
the core to a depth of 11 mm to compress or compact the core 22
into a dense end plug 24 of 4 mm thickness as shown in FIG. 6. It
will be appreciated that the cylindrical wall 21 will remain
unaffected by this operation and will be of the same density as the
material forming the plug. However the end plug 24 is arranged to
be of a density greater than that of the wall 21. Since the core 22
is distinct from and not integral with the cylindrical wall 21 of
blank 20 no cutting action is required in forming the plug shown in
FIG. 6, and a simple plunging action is all that is required. Such
an arrangement is simpler than that shown in FIG. 4 since no
tearing is experienced and a cleaner and a more satisfactory plug
is achieved. Sealing of the end plug is achieved in this embodiment
by an expansion of the plug diameter during the compression
longitudinally, thus sealing the plug within the cylindrical wall
21.
In the embodiment described with reference to FIGS. 5 and 6 the
core material 22 need not be the same as that forming the wall 21.
Although in the preferred embodiment described above both materials
are cellulose acetate of different packing densitities, it will be
appreciated that the core material could be different from that
forming the wall 21. Of course neither need be cellulose acetate.
Thus suitable materials could be a foamed synthetic resin or
another synthetic fibre.
Referring to FIG. 7 there is shown yet another method of achieving
a filter plug according to the present invention. The method is
similar to that shown in FIGS. 5 and 6 (but can be adapted to be
similar to that shown in FIGS. 3 and 4) but in which a double
length filter rod is plunged from both ends simultaneously whereby
a central dense wall 30 is formed with two hollow cores 31 and 32.
After the plunging operation, the filter plug is separated by
severing at 33 to form two filter plugs in accordance with the
present invention. The preferred method of achieving this dual
length filter is in accordance with the method described with
reference to FIGS. 5 and 6 since no cutting or tearing action is
necessary. The cutting action of FIGS. 3 and 4 can however be
employed if required. It will be appreciated that no lower support
is required for the filter plug during the plunging operation since
the opposed forces of the two plungers 34 will balance.
One form of apparatus suitable for producing a dual length filter
plug similar to that shown in FIG. 7 is shown in FIG. 8. This
apparatus comprises a mounting plate 60 attached to the frame of a
machine and having mounted thereon a cylindrical housing 61 with
fixed end plate 62 into the centre of which is rigidly fixed by
nuts 63 one end of a stationary shaft 64. To the other end of the
stationary shaft 64 is secured a stationary cam plate 65, a key 66
and nut 67 being employed to secure the cam plate 65 to the shaft
64.
Fixed to the inner face of mounting plate 60 is an annular cam
plate 70. A dowel pin 71 locates the cam plate 70 relative to the
mounting plate 60 and a number of studs 72 secures the cam plate 70
to the mounting plate 60. A cam surface 73 on the inner face of
plate 70 extends adjacent the periphery of cam plate 70 starting at
the top dead centre of the cam plate (i.e. at location M on FIG. 9)
with zero rise and continuing to the bottom dead centre position
(i.e. at location N in FIG. 9).
The maximum rise, at position N, is indicated by boss 74 in FIG. 8.
At this point the cam is stepped, the remainder of the cam plate
from N to M (travelling anticlockwise)being planar with no cam
surface.
Cam plate 65 is similarly provided on its inner face with a cam
surface 79 identical in form to cam surface 73. Cam surface 79
rises to a maximum from position M to N and is there stepped to
zero for the remainder of the plate.
Also mounted on the inner face of the stationary cam plate 65 is a
stationary annular carbon pad 77 provided on its inner face with an
annular groove 78. A pipe 80 connected to a source of vacuum or
suction (not shown) communicates with the annular groove 78 at
position M.
Mounted upon the stationary shaft 64 by needle bearings 81 and 82
is a drive shaft 83 provided at one end with a drive gear 84
connected to a drive source (not shown). Keyed by key 85 to the
drive shaft 83 is a composite solid drum formed primarily of three
disc segments 86, 87 and 88 fixed rigidly together (by means not
shown) and doweled by dowel pin 90 to ensure accurate relative
location. The central disc 87 is provided at its periphery with 12
equi-spaced semi cylindrical flutes or slots 91 (see FIG. 9) each
of the correct length and diameter to accommodate a dual length
filter plug blank 99 e.g. 30 mm long and 8 mm diameter.
Communicating with each slot 91 is a plurality of channels 92 which
in turn communicate with a common air duct 93 which extends through
disc 88 and seals against groove 78 in the annular carbon pad 77.
The annular groove 78 in the annular carbon pad 77 extends from
immediately before top dead centre position i.e. from position L as
shown in FIG. 9 until the bottom dead centre position i.e. position
N, extending in an anti-clockwise direction as indicated by arrow
P. For the remainder of the circumference i.e. from N to L the
channel 78 is blanked off. Thus vacuum will be applied through the
channels 92 to the semi cylindrical flutes or grooves 91 from
location L until location N in order to secure and hold dual length
filter plug blanks within the grooves during rotation of the drum.
A hopper (not shown) disposed with its outlet between locations L
and M as viewed in FIG. 9 is arranged to deposit dual length filter
plug blanks into the grooves 91 as they pass the location between L
and M as disc 87 rotates.
Disposed in each of the discs 86 and 88 are twelve equi-spaced
plungers 100, 101 respectively. The plungers are housed within
holes 102 and 103 respectively and in discs 86 and 88. The ends of
the plungers project to the cam plates 70 and 65 respectively and
bear against the cam surfaces 73 and 79. The plungers 100 and 101
are urged into contact with cam plates 70 and 65 by springs 104 and
105 respectively. Cylindrical tools 106 and 107 slide within
locating holes provided in annular guide plates 108 and 110 between
the full line positions and the broken line positions shown in FIG.
8 as the cylinder moves from the top dead centre position M
illustrated in FIG. 9 to the bottom dead position N illustrated in
FIG. 9. For a 30 mm. plug blank the tools are arranged to penetrate
the ends of the blank for a distance of say 11 mm, leaving an 8 mm
dense wall centrally of the plug. When the 30 mm plug is severed
into two 15 mm plugs the central core will form a 4 mm dense end
wall for each plug in the manner described with reference to FIG.
7.
In use, dual length filter plug blanks are fed into slots 91
between locations L and M as seen in FIG. 9, suction being applied
to the slots 91 between the position L and N whereby the filter
plug blanks are held in the grooves. As the cylinder rotates from
location M to N (in an anti-clockwise direction as viewed in FIG.
9) the plungers 100 and 101 will be cammed inwardly of the filter
plug blank whereby the tools 106 and 107 will compact the core of
the blank from either end to form a central dense end wall. At the
location N the cam surfaces are stepped whereby the plungers spring
back to their retracted (full line) positions withdrawing the tools
from the filter plugs. Also at location N, the suction to grooves
91 is cut off. Immediately after location N the compacted plugs are
free of the grooves 91.
Although as described, the cam surfaces and vacuum source are
applied to the drum for more than half its revolution, it will be
appreciated that either or both these actions could be operable for
a shorter or longer period, depending upon the desired operation of
the equipment.
The drum described above with reference to FIGS. 8 and 9 preferably
forms part of a filter tip cigarette making machine and may for
example replace the filter drum on a Hauni KFZ filter cigarette
making machine. In such a machine the compacted dual length filter
rods leaving the drum between locations N and Q as seen in FIG. 9
will be transferred to a drum containing two cigarette lengths
located on either side of each dual length filter plug; these will
be rolled in a paper wrapper to form two filter cigarettes joined
end to end and will subsequently be severed to form two single
filter tip cigarettes
The filter plugs made in accordance with the present invention can
be used in a variety of ways. It will be appreciated that the plug
having one end blocked by a wall will present one flat surface
which can be placed at the mouth end of the cigarette to provide a
pleasing appearance. In this event the open end of the cylindrical
plug will abut the tobacco rod of the cigarette. Alternatively, the
open end of the filter rod can be at the mouth end of the cigarette
the plug of the filter rod then being in abutment with the tobacco
rod of the cigarette.
To achieve maximum efficiency from filters according to the present
invention it is desirable that tobacco smoke passing through the
walls of the filter should be permitted to pass radially through
the walls rather than be forced to pass longitudinally through the
walls. Should the filter plugs be wrapped by impermeable paper or
relatively impermeable paper, as in conventional cigarette, the
pressure drop of the filters may well be far in excess of that
which is normally acceptable to the smoker since smoke will be
forced to travel longitudinally through the wall of the filter.
To enable smoke to pass through the cylindrical wall radially of
the plug, air ducts or passages must be provided externally of the
filter plug through which the smoke can pass. Three ways in which
this can be achieved are shown in FIGS. 10, 11 and 12.
Referring to FIG. 10 there is shown the mouth end of a cigarette
including a filter plug 35 in accordance with the present
invention. Plug 35 has a cylindrical wall 40 and a denser end wall
51. The plug is wrapped by a dual layer paper wrapper comprising an
external cylindrical sheath 41 and an internal corrugated sheath
42. The internal corrugated sheath 42 contacts both the external
sheath 41 and the external surface of the cylindrical wall 40. Thus
air channels are provided between the corrugations of the sheath 42
and the external surface of the cylindrical wall 40. Smoke which
passes through the core of the filter 35 passed radially outwardly
through wall 40 and to the smokers mouth along these longitudinal
ducts or air channels.
Referring to FIG. 11 there is shown an alternative embodiment
including a filter plug 36 according to the present invention
comprising a cylindrical wall 45 and a denser end wall 52. The plug
is wrapped by a single corrugated or longitudinally fluted
cigarette wrapper 46. Again, air passages are provided between the
flutes of the wrapper 46 and the external surface of the
cylindrical wall 45 providing passageways for the smoke passing
through the wall of the filter to pass to the smokers mouth. Such
an arrangement of fluted or corrugated external wrapper for a
cigarette also provides less surface contact between the cigarette
wrapper and the smokers lips preventing sticking and also provides
passage in the external corrugations of the paper in which ambient
air can be drawn into the smokers mouth.
Referring now to FIG. 12 there is shown yet another arrangement
including a filter plug 37 in accordance with the present invention
comprising a cylindrical wall 48 and a denser end wall 53. The plug
is provided with an external longitudinally fluted surface 49 and
this is wrapped by a cylindrical wrapper 50. Again, longitudinal
air channels are provided between the external flutes of the
surface 49 of wall 48 and the wrapper 50 allowing smoke to pass to
the smokers mouth.
A method of making the fluted filter plug blanks from which
elements 48 can be formed is described and claimed in cognate U.K.
patent applications 8462/70 and 23854/70.
It will be appreciated that, in the embodiments of FIGS. 10-12, the
filter plug could in each instance be reversed to place the end
walls or plugs 51, 52 and 53 respectively in abutment with the
tobacco rods 54, 55 and 56 respectively in which case an open
cylindrical end would be presented to the smokers mouth. The open
end could be blocked by an end plug but, unlike the relatively
dense plug 51, 52 or 53, this plug would be provided merely to
close the end of the cylinder and would be of a material providing
a less dense surface than that of the wall of the cylinder of the
filter plug thus inducing the smoke to flow through this plug into
the smokers mouth.
It will also be appreciated that the filter plugs according to the
present invention need not be hollow but could be packed with a
filter material which is less dense than that of the cylindrical
wall. Nevertheless the cylindrical plug must still be provided with
an end wall which is denser than that of the wall of the plug thus
inhibiting flow and forcing the tobacco smoke to pass radially
through the wall of the cylinder.
The material from which filter plugs according to the present
invention are made is not important although cellulose acetate and
foamed and other fibrous synthetic resins are preferred.
In view of the difficulty of wrapping filter plugs with paper
having convolutions or corrugations or flutes therein as shown for
example in the embodiments of FIGS. 10 and 11, the preferred
embodiment according to the present invention is that shown in FIG.
12 in which the longitudinal flutes or corrugations are already
extruded within the cellulose acetate rod forming the filter plug
and this is merely wrapped in a conventional cylindrical sheath.
Alternative arrangements can of course be provided. Thus the
external surface of the filter could be dimpled or otherwise
roughened merely to provide proturberances which space the
overlying wrapper from the surface of the filter plug thereby
providing air passages to enable the smoke to pass to the smokers
mouth.
Test results with filter plugs according to the present invention
indicate that more efficient plugs are provided even with pressure
drops the same as these of conventional plugs. Cellulose acetate
plugs of the type described with reference to FIG. 7 but of 40mm.
overall lengths were compacted to a core depth of 15 mm. either
and, leaving a central wall of 10 mm. These plugs were cut into two
hollow cylindrical sections, each 20 mm. long with 5 mm. dense end
wall and were tested for pressure drop and efficiency. The results
of three different typical samples, having different core densities
before plunging, are quoted in Table 1.
TABLE 1
Results a b c d Sample 1 0.226 1.3 37.5 9.0 2 0.276 1.6 42.1 12.0 3
0.348 1.2 41.8 8.0
In each Sample the outer cylinder density was the same as that of a
conventional plug of cellulose acetate. The results tabulated
are:
a. Density of inner core before compacting (gm. per. cc.)
b. Pressure drop of plug after compacting (cm. of water).
c. Efficiency of compacted plugs (%).
d. Efficiency of conventional plug of same pressure drop (%)
Similar tests on conventional plain cellulose acetate plugs of the
same pressure drops are also quoted, from which it will be seen
that a considerable increase in efficiency is obtained with the
compacted rods.
Thus with filter plugs in accordance with the present invention it
is envisaged that much more efficient plugs can be provided but
having the same pressure drop as those conventionally provided with
present day filter plugs. By increasing the pressure drop of the
filter, yet further increases in efficiency can be achieved. Rather
than make compacted plugs having the same pressure drop as
conventional plugs, it is possible to make plugs of the same
efficiency, in which case the compacted plugs will have a lower
pressure drop compared with conventional plugs.
Due to the increase in efficiency it would be possible for example
to replace current dual-plug filters -- e.g. of Myria (MYRIA is a
Registered Trade Mark) and cellulose acetate, with single plug
filters made of one material, thus providing considerable saving in
cost and handling.
Substantial decreases in the pressure drop of the plug as a whole
and/or substantial increases in efficiency can be achieved with
filters according to the present invention compa ed with
conventional filters of the same material and external
dimensions.
* * * * *