Method and apparatus for making tobacco smoke filters

Tobacco smoke filters and methods and means for making same wherein the products have a composite substantially cylindrical inner member formed from two semi-cylindrical inner elements and overwrapped with a common plug wrap. The composite inner member has a discrete inner cavity formed in each semi-cylindrical element and a composite cavity formed by a depressed portion in each semi-cylindrical element. A substantially smooth outer surface is provided on the composite inner member for attaching a conventional plug wrap without the need for an internal glue line. Separate cylindrical elements are reformed into semi-cylindrical elements and crimped to provide depressed pockets, following which the semi-cylindrical elements are mated and overwrapped to produce the final product.

This invention relates to the production of filter means, and relates more 
particularly to tobacco smoke filter elements. More specifically, the 
instant inventive concepts are primarily concerned with producing filter 
means for cigarettes, although the products of this invention are 
generally useful as filters, particularly for tobacco smoking means, 
whether they be cigarettes, cigars, pipes or the like. Since filters for 
cigarettes are particularly commercially important, the basic embodiments 
of the instant invention will be discussed as they relate to the 
production of filtered cigarettes. 
Various prior art techniques are known for making filters for use in 
connection with cigarettes and the like, although the resultant products, 
in general, have one or more disadvantages. Perhaps the most important 
property of the filter means is its efficiency, that is, its ability to 
remove undesirable constituents from tobacco smoke. Filtration efficiency 
is ordinarily measured in terms of the percentage of total particulate 
matter (TPM) removed from the smoke, although there is also some concern 
for the percentage of gas phase constituents which a filter means is 
capable of removing. While filtration efficiency is perhaps the most 
important property of cigarette filter means, other properties must also 
be considered, including pressure drop, taste, hardness, appearance and 
cost. It is necessary to produce a filter which satisfies commercial 
requirements in each of these areas. Frequently, certain of these 
properties must be compromised in order to satisfy the need for others. 
For example, the most commonly utilized cellulose acetate filter means has 
a relatively low filtration efficiency since increased efficiency can only 
be obtained either by increasing the density of the filter material or the 
length of the filter element, both of which produce a pressure drop across 
the filter which is excessive and unacceptable from a commercial 
standpoint. While various suggestions have been made for the production of 
filter means which have improved filtering properties, most prior art 
developments have not been commercially acceptable either because the 
resulting filter means have been found to have objectionable "taste" 
characteristics whereby cigarettes provided with such filtering means fail 
to satisfy a large segment of the smoking public, or because the 
techniques and/or the materials utilized in the production of such filter 
means have increased the cost excessively. 
High filtration efficiency is considered by the industry to be removal of 
60% or more of total particulate matter. Cigarette filters having such 
properties are presently being produced in accordance with the teachings 
of U.S. Pat. Nos. 3,533,416, 3,599,646, 3,637,447, 3,648,711, 3,805,801 
and 3,810,477, all of which are commonly assigned with the instant 
application. The disclosures of these prior art patents are incorporated 
herein in the entirety by reference. 
However, it would be commercially desirable to be able to produce yet 
another tobacco smoke filter means having high filtration efficiency, low 
pressure drop and other satisfactory commercial properties. 
Therefore, it is a primary object of this invention to provide a cigarette 
filter means or the like and a method and means for manufacturing same 
wherein the product has satisfactory pressure drop and other commercial 
requirements, and which may have both solid and gas phase filtration 
properties. 
A further object of this invention is the provision of a cigarette filter 
or the like which has an inner member provided with a multiplicity of 
cavities to improve the flow path of tabacco smoke and enable greater 
utility of the filtering material from which it is made, while 
simultaneously permitting a conventional plug wrap to be used as an outer 
member which is substantially continuously supported throughout its length 
by the inner member so as to avoid the need for an internal glue line as 
has been required by the prior art techniques. 
Yet another object of this invention is the provision of a filter means of 
the type described wherein, if desired, one or more of the cavities can be 
at least partially filled by a further smoke-modifying material such as 
activated carbon or the like. 
Still another object of this invention is the provision of a cigarette 
smoke filter having a unique appearance enabling unusual esthetic effects 
to be produced.

Like reference characters refer to like parts throughout the several views 
of the drawings. 
Referring now to the drawings, and more particularly to FIG. 1, a filtered 
cigarette according to the instant inventive concepts is designated 
generally by the reference numeral 20 and comprises basically a tobacco 
rod shown partially at 22 and a filter element according to one embodiment 
of this invention designated generally by the reference numeral 24, a 
conventional tipping overwrap being shown in dotted lines at 26 securing 
the tobacco rod and the filter element in end-to-end relationship 
according to well known prior art techniques. 
The filter element 24 comprises basically an axially elongated, hollow, 
outer member 28 formed by conventional plug wrap as will be explained 
hereinafter in more detail, and an axially elongated, substantially 
cylindrical, composite inner member designated generally by the reference 
numeral 30 disposed within the outer member 28. 
The composite, substantially cylindrical, inner member 30 is formed of a 
pair of mating, axially elongated, hollow, semi-cylindrical inner elements 
32, 34, each of which is preferably and primarily formed from a continuous 
tow of cellulose acetate filamentary material, although other filtering 
material may be used with slight modifications. For example, filmentary 
tow formed of other materials such as polyethylene, polypropylene and the 
like or even non-woven stable filters of the type described in some detail 
in U.S. Pat. Nos. 3,297,041 and 3,552,400, also commonly assigned, the 
disclosures of which are incorporated herein by reference, may also be 
used. In fact, it is possible to produce filter elements according to this 
invention from an extruded, open-celled, foam material, such as cellulose 
acetate foam or the like. However, since cellulose acetate filamentary tow 
is the presently preferred material from a commercial standpoint, the 
remainder of this specification will be directed to the use of such 
material. 
Thus, each of the semi-cylindrical elements 32, 34 are preferably formed of 
crimped filamentary cellulose acetate members bonded together at their 
contact points to form a smoke-permeable element defining a tortuous path 
for passage of smoke therethrough. Filtering material of this nature is 
well known, as are techniques for producing same. 
As will be seen particularly from FIGS. 1 and 4, integral circumferentially 
continuous peripheral portions of the outer surface of the composite inner 
member 30 are juxtaposed to portions of the inner surface of the outer 
member 28 to at least substantially preclude axial passage of smoke across 
the area therebetween. By thus providing substantially uniform continuous 
support for the outer member 28 over its entire length it is possible to 
use a lighter weight plug wrap for the outer member 28 than is required 
when significant portions of the inner member are spaced from the outer 
member as, for example, in a filter of the type shown in U.S. Pat. No. 
3,533,416. Moreover, this substantially uniform support precludes the need 
for an internal glue line between the inner and outer members as has been 
necessary with prior art techniques. 
It will be seen that each of the semi-cylindrical inner members 32,34 
define discrete inner cavities, 36,38, with depressed portions 40,42 of 
the semi-cylindrical elements 32,34, respectively, together forming a 
composite cavity 44 spaced from the discrete inner cavities 36,38. 
Of course, it is possible to reverse the filter element 24 in the filtered 
cigarette 20 so that the composite inner cavity 44 is at the mouthpiece 
end of the filtered cigarette with the discrete cavities 36,38 being 
juxtaposed to the tobacco section 22. 
In FIG. 3 a continuous rod 50 made up of a multiplicity of integrally 
connected filter elements of the type shown at 24 in FIG. 1 will be seen. 
The rod 50 may be severed transversely along the lines 52,54 to produce 
individual filter elements such as shown at 24. Of course, the rod could 
be severed at other locations to produce filter elements of multiple 
length. For example, the rod could be severed at 52 and 52a to produce a 
double filter having a totally enclosed composite inner cavity 44 or at 54 
and 54a to produce a double filter having totally enclosed discrete inner 
cavities 36,38. Moreover, it is common practice to initially produce 
double filters which are then secured to two tobacco sections by a common 
tipping overwrap following which individual filtered cigarettes are formed 
by severing the double filter at its midpoint. 
Although in the embodiment of FIGS. 1, 3 and 4 the cavities 36,38 and 44 
have been shown as empty, it is possible to at least partially fill one or 
more of these cavities with a further smoke-modifying material such as, 
for example, activated carbon. In FIG. 5, a modified embodiment of the 
instant inventive concept is shown wherein the discrete inner cavities are 
at least partially filled with such material and in FIG. 6 a further 
modified form is shown in which the composite inner cavity includes such 
further smoke-modifying material. Since these embodiments are basically 
identical to the embodiment of FIG. 1, similar reference numerals have 
been used, with the embodiment of FIG. 5 carrying a suffix "a" and the 
embodiment of FIG. 6 carrying a suffix "b". Further, it is believed 
obvious that all of the cavities could be filled in an individual filter 
element. Moreover, although activated carbon and loose granules have been 
suggested as a further smoke-modifying material, other conventional 
materials could be substituted therefor, including activated carbon or 
other sorbent particles bonded by small particles of polyethylene or the 
like or loose sorbent particles of other materials such as silica gel or 
the like. 
These further smoke-modifying materials added gas phase activity to the 
filter element, enabling the removal of undesirable gas phase constituents 
while the filtering material of the composite inner member itself 
functions as the primary filter for the solid phase constituents of the 
tobacco smoke. In addition to adding gas phase capability to the filter 
element, inclusion of materials of this nature in the cavities produces a 
filter having a unique appearance. 
Reference is now made particularly to FIGS. 2 and 7-9 for the overall 
method and means utilized in producing filter elements in accordance with 
this invention. The initial phases of the production line are quite 
similar in many respects to the concepts shown and described in detail in 
U.S. Pat. No. 3,637,447 referred to previously. According to preferred 
embodiments of this invention separate sources of filter material in the 
form of continuous filamentary tows 60,62, each of which includes a 
multiplicity of bondable fibrous members activated by contact with a hot 
fluid such as steam, are provided. These materials may be the same, if 
desired, or different filtering materials could be utilized for production 
of the individual semi-cylindrical elements to be described further 
hereinafter. However, for simplicity, it will be presumed that in each 
instance, a continuous cellulose acetate filamentary tow is being 
utilized. In each instance, the filtering material is continuously passed 
into and through an elongated bonding zone which may comprise conventional 
stuffer jets 64,66 and steam heads 68,70 similar in nature to those shown 
in various of the abovementioned prior art patents. Details of the stuffer 
jet and steam head 66,70 are shown in FIG. 7, it being understood that 
similar means are provided for processing the filtering material 60. A 
mandrel 72 is positioned generally axially of the bonding zone to define 
an annular space through which the filtering material 62 must pass. Thus, 
in the steam head 70 the fibrous members of the filter material 62 are 
contacted by the bond activating agent, namely, steam, to produce a 
smoke-permeable annular wall of bonded fibrous members designated 
generally by the reference numeral 74 in FIG. 7. This cylindrical element 
74 is fed into a reforming means 78 shown in detail in FIGS. 7 and 8 (a 
similar reforming means 80 being provided for the filtering material 60). 
The reforming means 78 comprises a rotatably supported reforming wheel 82 
having spaced humps 84 and intermediate flat sections 86 which engage the 
cylindrical element 74 as it passes through the reforming means 78, the 
flattened sections 86 reforming the substantially cylindrical element 74 
into a semi-cylindrical element with the humps 84 producing spaced pockets 
therein to thereby form the integral inner cavities 36,38 and a portion of 
what is to become the composite cavities 44. If necessary, the 
substantially cylindrical inner element 74 may be contacted with steam in 
the reforming means 78 in order to soften this element and facilitate the 
reforming by the wheel 82. 
If it is desired to incorporate a further smokemodifying material into the 
discrete inner cavities 34a, 36a as shown in FIG. 5, such material may be 
intermittently fed from a source of same shown in dotted lines at 90 in 
FIG. 7 through the interior of a hollow mandrel 72. Similarly, if it is 
desired to provide a further smoke-modifying material within the composite 
inner cavity 44b as shown in FIG. 6, such material may be fed from a 
source of same shown in dotted lines at 92 in FIG. 7 into the pocket 
formed by the humps 84 prior to integrating the individual 
semi-cylindrical elements 32,34. 
After reforming, the semi-cylindrical elements 32,34 can be cooled in 
conventional cooling heads illustratively shown at 84,96 in FIG. 2 and 
then passed to and through a rod guide 100 and a further steam head 102, 
shown in detail in FIG. 9, and a cooling head 104 to mate the 
semicylindrical inner elements 32,34 and reform them into a true 
cylindrical shape to produce the substantially cylindrical composite inner 
member 30. 
A garniture is shown at 106 in FIG. 2 to provide a continuous pulling 
mechanism drawing all of the elements through the processing steps and to 
simultaneously overwrap the composite inner member 30 with a conventional 
plug wrap 108 to form the outer member 28. If desired, or if necessary, 
separate pulling means may be provided for the individual semi-cylindrical 
inner elements 32,34 such means not being shown for illustrative 
convenience. 
Finally, the rod is severed transversely at selected locations in a cutting 
means shown schematically at 110 in FIG. 2. 
The following data compares certain characteristics of products made 
according to the instant inventive concepts designated as "I" and "II" 
with products produced according to prior art techniques, a single filter 
element of the type shown, for example, in U.S. Pat. No. 3,637,447 being 
designated as "III" and a double filter element of the type shown in U.S. 
Pat. No. 3,805,801 being designated as "IV" in the table below. 
______________________________________ 
Percent 
Type Weight Pressure Drop 
Retention 
______________________________________ 
I 18.2 gms 1.8" 66.2 
II 16.3 gms 3.5" 75.0 
III 16.5 gms 2.8" 69 
IV 13.4 gms 2.8" 65 
______________________________________ 
It will be seen from the above that filter elements prepared according to 
the instant inventive concepts can be produced having favorable pressure 
drop characteristics as well as good filtration efficiency. Other 
commercially significant properties such as hardness, taste and the like 
also compare favorably with prior art filters. Moreover, the filter of 
this invention has the particular advantage of being able to readily 
incorporate further smoke-modifying materials such as activated carbon or 
the like and, additionally, to provide unique esthetic appearances. 
It will now be seen that there is herein provided a smoke filter and method 
and means for manufacturing same which satisfies the various objectives 
set forth previously, and which provides significant advantages of a 
commercial nature. While this invention has been described with reference 
to presently preferred exemplary embodiments thereof, it should be 
understood that the invention is not limited thereto, but may be variously 
practiced within the scope of the following claims. 
However, although the filter product of this invention has been shown 
without cavities between the inner surface of the outer member and the 
outer surface of the composite inner member, it should be understood that 
limited external cavities of the type shown and described in copending 
U.S. patent application Ser. No. 627,858 filed Oct. 31, 1975, the 
disclosure of which is incorporated herein in its entirety by reference, 
can be provided to enhance the smoke flow characteristics while still 
permitting the use of conventional plug wrap and avoiding the need for an 
internal glue line.