Manufacture of tobacco smoke filters

Apparatus and method are described for manufacturing a filter rod from a continuous multifilament filter tow which is treated with a smoke-modifying agent during the filter rod manufacturing process.

TECHNICAL FIELD 
This invention relates to the processing of a continuous, multifilament 
filter tow for the manufacture of tobacco smoke filters. 
BACKGROUND ART 
The manufacture of tobacco smoke filters from a continuous multifilament 
filter tow generally involves processing steps which include separation of 
the individual filaments (i.e., "opening up" of the filter tow), the 
application of plasticizer and other additives to the "opened up" tow and 
the formation of a continuous filter rod from the treated filter tow. The 
uniformity and filtering characteristics of the resulting filter rod are 
largely determined by the effectiveness of these tow processing steps. The 
processing steps become particularly critical when the applied additives 
include flavoring materials or other active agents which modify the 
tobacco smoke as it passes through the filter 
U.S. Pat. No. 2,966,198 discloses apparatus for applying aqueous solutions 
of cellulose derivatives to filter tow as the tow is subjected to a 
turbulent current of air. Although this apparatus may be suitable for 
applying solutions of film-forming binders to the tow, it does not provide 
the degree of control required for producing a uniform filter rod. 
The application of various flavoring materials to tobacco smoke filters is 
disclosed in U.S. Pat. No. 3,144,024 but apparatus for incorporating such 
materials is not specifically described. 
U.S. Pat. Nos. 3,371,000 and 3,847,064 disclose methods and apparatus for 
making tobacco smoke filters containing added filtration materials such as 
activated carbon. Various apparatus designs are described which inject a 
slurry of activated carbon into the filter tow at spaced intervals. 
Closely related to these patents are U.S. Pat. Nos. 3,095,343 and 
3,774,508 which describe methods and apparatus for shaping filter tow into 
a hollow cylindrical rod by positioning a mandrel concentrically in the 
path of the moving filter tow and injecting steam into the filter tow. 
In U.S. Pat. Nos. 3,779,787 and 3,853,039 an additive is introduced into a 
filter rod by piercing the rod with a needle and submerging the pierced 
rod in a liquid additive bath or, alternatively, by directing a jet of 
liquid additive against the rod with sufficient force to impregnate the 
filter rod. 
Another method for incorporating additives into tobacco smoke filters is 
disclosed in U.S. Pat. No. 4,281,671 and involves combining filter tow and 
a thread impregnated with a smoke-modifying agent in the manufacture of a 
tobacco smoke filter. The surface area presented by the impregnated thread 
is quite limited, however, and the portion of tobacco smoke contacting the 
thread is also correspondingly quite limited. 
A dual filter construction is disclosed in U.S. Pat. No. 3,313,306 which is 
formed from a fibrous filter tow that may optionally be treated with 
additives. The filter tow is formed into an elongated rod which is 
compressed at spaced locations to give a compacted core of tow that is 
provided with an annular sheath of a second filter material such as carbon 
granules at the spaced locations. 
U.S. Pat. No. 4,291,711 discloses a filter formed from reconstituted 
tobacco and a fibrous filter tow with either material constituting a 
central longitudinal core that is enveloped by an annular sheath of the 
other material. The reconstituted tobacco may optionally be treated with 
tobacco flavorants. 
The manufacture of filter rods from continuous multifilament filter tow 
typically involves moving the filter tow in a generally longitudinal 
direction through a succession of treatment steps designed to align and 
spread apart the individual filaments by mechanical and/or pneumatic means 
so that plasticizers and other additives may be applied to the aligned and 
spread filter tow before the tow is gathered and formed into a 
predetermined shape such as a substantially cylindrical rod. The 
processing steps may also include the application of paper wrap to the 
filter tow to produce a paper wrapped filter rod. When the manufacture of 
filter rods also involves incorporation of flavoring materials, the 
application of flavoring materials to the filter tow has heretofore 
generally involved dissolving such materials in the plasticizer. Such a 
method of application, however, does not provide a very precise degree of 
control over the levels of flavoring materials applied to the filter tow 
and it also results in contamination of the apparatus used for applying 
plasticizer. The contamination problem is particularly objectionable when 
filter rods containing different flavoring materials are to be produced 
using the same apparatus. 
Current commercial manufacture of filter rods from filter tow involves two 
basic techniques for pretreatment of the tow prior to formation of the 
filter rod. One technique uses pneumatic banding jets and cooperating sets 
of rolls including circumferentially grooved rolls adapted to contact and 
to spread and stretch the filter tow thereby transforming the tow into a 
flat wide band that is then passed through a chamber where plasticizer is 
applied to the band of tow by spray or other suitable means. The other 
technique employs a pneumatic banding jet to create a narrow flat band of 
tow that is drawn across wick-type applicators which deposit plasticizer 
on both sides of the band of tow before the tow is passed through a jet 
device for stretching, aligning and blooming the tow. In both techniques 
the pretreated filter tow, comprising a longitudinally oriented assemblage 
of filaments having individual filaments of the tow in substantial 
alignment, is fed into a converging horn or funnel located adjacent to the 
entrance of filter rod-forming means. The converging horn or funnel 
gathers and compresses the filter tow into a rounded, rope-like 
configuration and a tongue device located between the converging funnel 
and rod-forming means applies further converging and compressing forces to 
the filter tow as the tow enters the garniture of the rod-forming means. 
The rod-forming means may be provided with means for heating the advancing 
filter tow sufficiently to produce a stable, continuous non-wrapped filter 
rod or it may be provided with means for wrapping the filter tow in a 
continuous paper web to produce a continuous paper-wrapped filter rod. In 
some commercial filter rod-forming operations, a stuffer jet or transport 
jet is utilized as converging means for gathering the flat band of treated 
filter tow and transforming it into a loosely compacted rope-like 
configuration that is directed to the rod-forming means. The stuffer jet 
or transport jet is usually located adjacent the entrance to the 
rod-forming means. Stuffer jets or transport jets typically comprise a 
truncated cone-shaped device having a large end for receiving the 
advancing filter tow and a small end for discharging the filter tow with 
orifice means intermediate the large end and small end for directing a 
pressurized gaseous medium onto the advancing filter tow. 
BRIEF SUMMARY OF THE INVENTION 
This invention provides an improved method and apparatus for applying a 
smoke-modifying agent to a continuous multifilament filter tow in 
conjunction with the manufacture of tobacco smoke filters from the tow. 
It is a principal object of this invention to provide a method and 
apparatus for applying a smoke-modifying agent to a continuous 
multifilament filter tow subsequent to flexing and tensioning of the tow 
but prior to formation of the tow into a filter rod of predetermined 
shape. 
It is a further object of this invention to provide a method and apparatus 
for applying uniform amounts of a smoke-modifying agent to selected 
portions of a filter rod formed from a continuous multifilament filter 
tow. 
An additional object of this invention is to provide a method and apparatus 
for applying flavoring materials to a continuous multifilament filter tow 
in connection with the formation of a filter rod that is subsequently cut 
into individual filters for cigarettes. 
Yet a further object of this invention is to provide a tobacco smoke filter 
having a zone of flavoring materials selectively located to facilitate 
transfer of the flavoring materials to tobacco smoke passing through the 
filter. 
Other objects and advantages will be apparent from the detailed description 
which follows.

DETAILED DESCRIPTION OF THE INVENTION 
This invention provides a convenient and effective apparatus and method for 
applying a smoke-modifying agent to a continuous multifilament filter tow 
as the tow is being formed into a continuous filter rod that is 
subsequently cut into segments and used for filtering tobacco smoke. The 
invention is particularly suitable for the application of flavoring 
materials to the filter tow although other materials such as plasticizers 
and smoke filtration agents may also be applied. The term "smoke-modifying 
agent" as used herein is not considered to include filter tow plasticizing 
agents such as triacetin but does include flavoring materials and agents 
capable of selectively removing certain tobacco smoke components from the 
smoke as it passes through the filter. The manner in which the additive is 
applied also lends itself to controlling the location of the applied 
additive in the formed filter rod since processing arrangements can be 
selected for applying the additive under relatively non-turbulent 
conditions. 
The smoke-modifying agents used in connection with the present invention 
are preferably compounds or mixtures of compounds which exist in the 
liquid or vapor state at the temperature and pressure conditions 
prevailing during application of the agents to the tow. The agents may 
also take the form of solutions, emulsions or suspensions of solid or 
liquid or microencapsulated organic flavoring compounds in water, 
triacetin, ethanol, propylene glycol or other suitable liquid carrier 
media. A further variation involves the application of a volatile additive 
in vapor form to the filter tow under conditions that would permit 
condensation of the additive on the tow, absorption of the additive vapors 
by plasticizer previously applied to the tow or adsorption of the additive 
vapors by the filter tow or other agents associated with the tow. 
Regardless of the manner in which the smoke-modifying agents are applied 
to the filter tow, the quantity of agent injected into the tow, including 
any liquid carrier media used, will normally not exceed 15 percent by 
weight based on the total weight of the filter tow being processed and, 
preferably, will not exceed 10 percent. Solutions of flavoring materials 
are typically applied at levels of 5 percent by weight or less based on 
the weight of tow being processed. 
The apparatus used in accordance with this invention for manufacturing a 
filter rod containing a smoke-modifying agent comprises (a) means for 
moving a continuous multifilament filter tow through a succession of 
treatment steps with the direction of movement coinciding generally with 
the longitudinal axis of the filter tow, (b) means for transforming the 
moving filter tow into a longitudinally oriented assemblage of filaments 
having individual filaments of the tow in substantial alignment, (c) 
converging means for gathering and compressing the longitudinally oriented 
assemblage of filaments to produce a longitudinally oriented filter tow 
with a rope-like configuration, (d) nozzle means associated with said 
converging means and positioned in the path of the moving filter tow so 
that the nozzle means is substantially enveloped by the moving filter tow 
in encircling fashion, (e) means for supplying controlled amounts of a 
smoke-modifying agent to the nozzle means for application of the agent to 
the moving filter tow and (f) rod-forming means adjacent to the converging 
means adapted to receive the longitudinally oriented, rope-like filter tow 
treated with the smoke-modifying agent and to form the filter tow into a 
filter rod having a predetermined shape. 
The basic arrangement described herein for processing the filter tow is 
conventional and this provides one of the principal advantages of the 
present invention. The modifications to the tow processing apparatus 
required for incorporating the improvements of this invention are not 
disruptive and do not interfere to any significant degree with operation 
of the apparatus in the conventional manner, if desired. This invention, 
therefore, provides great flexibility in operation because the mode of 
operation can be changed almost instantaneously. 
The principal feature of this invention involves the positioning of nozzle 
means in the path of a moving filter tow downstream of a point at which 
the filter tow has been sufficiently gathered and compressed by converging 
means to envelop the nozzle means in substantially encircling fashion. 
Since the advancing filter tow substantially envelops the nozzle means in 
encircling fashion, it is apparent that the physical size of the nozzle 
means or spraying device must be limited in order to minimize interference 
with movement of the filter tow. It is also important that the advancing 
filter tow be gathered and at least partially compressed at the point 
where it envelops the nozzle means in encircling fashion. Accordingly, the 
modified apparatus of this invention generally includes conduit means 
associated with the nozzle means and the longitudinal axis of a major 
portion of the combined conduit and nozzle means that is positioned in the 
path of the filter tow is in substantial longitudinal alignment with the 
longitudinal axis of the encircling filter tow. It is preferred that the 
cross-sectional area (i.e., a section transverse to the longitudinal axis) 
of the nozzle means as well as any portion of the associated conduit means 
enveloped by the filter tow not exceed about 25 percent of the transverse 
cross-sectional area of the filter tow-confining passageway which 
surrounds the nozzle means and associated conduit means. If the nozzle 
means comprises two or more spraying devices and conduit means associated 
therewith, the cross-sectional area of each will be correspondingly 
reduced so that the combined transverse cross-sectional area of the 
spraying devices and associated conduit means enveloped by the encircling 
tow will not exceed about 25 percent of the transverse cross-sectional 
area of the filter tow-confining passageway which surrounds the spraying 
devices and associated conduit means. 
The nozzle means and associated conduit means may be fabricated from any 
suitable material; however, metallic or plastic materials which are 
relatively rigid are preferred so that the nozzle means will remain in an 
essentially fixed position in the path of the filter tow. The conduit 
means with the nozzle means attached to the terminus thereof may, for 
example, extend into or through the converging horn a sufficient distance 
to position the nozzle means directly in the path of the filter tow as it 
moves toward the rod-forming means. The nozzle means and associated 
conduit means may also be positioned in the filter tow path within the 
tongue device adjoining the inlet zone of the rod-forming means or they 
may extend slightly beyond the termination point of the tongue device in 
the inlet zone of the rod-forming means. Alternatively, the nozzle means 
may be positioned within a stuffer jet or transport jet in the event such 
devices are used in processing the tow. When such jet devices are used, it 
is preferred that the nozzle means be positioned downstream of the orifice 
means employed in those devices. In all cases the nozzle means and 
associated conduit means should be in substantial longitudinal alignment 
with the longitudinal axis of the advancing filter tow and be securely 
anchored to a suitable fixed support to avoid excessive lateral movement 
of the nozzle means as the encircling filter tow moves past it. 
Various nozzle designs and arrangements may be used with this invention 
depending on the particular results desired. In those cases where a liquid 
additive, solution or suspension is being applied, it is preferred that 
the nozzle means be provided with a source of compressed gas that can be 
injected with the additive to effect atomization of the additive and to 
improve penetration of the additive into the filter tow filaments 
immediately surrounding the nozzle means. Distribution of the additive in 
the filter tow is also increased by employing nozzle means capable of 
generating a radial spray pattern that is substantially perpendicular to 
the longitudinal axis of the filter tow. 
It is apparent that the portion of the filter tow bundle treated with the 
smoke-modifying agents will determine the degree to which the 
smoke-modifying effect is perceived by the smoker. Accordingly, it is 
important that at least one percent of the filter tow bundle be treated 
with the additive to provide a significant effect on the smoke. Although 
the presently disclosed method of applying additive to filter tow is 
capable of achieving additive penetration throughout the filter tow 
bundle, total penetration of the filter tow bundle requires injection of 
the additive with a compressed gas under elevated pressures. As the 
pressure of the injected gas is increased, dissipation of the injected gas 
tends to interfere with the orderly movement and compaction of the filter 
tow as it enters the rod-forming garniture. Thus, the use of gas pressures 
in excess of 2500 grams per square centimeter in connection with the 
injection of additives should preferably be avoided. By limiting the gas 
pressures used for injecting the additives to 2500 g/cm.sup.2, the maximum 
penetration of additive into the filter tow leads to approximately 75 
percent of the filter tow bundle being treated. Since the additive 
distribution pattern achieved by this invention is generally cylindrical 
in shape with its longitudinal axis substantially parallel to the 
longitudinal axis of the formed filter rod, the additive-treated portion 
of the formed filter rod can also be expressed as a function of its 
cross-sectional area. Consequently, a cross-section that is perpendicular 
to the longitudinal axis of the formed filter rod may have between 1 and 
75 percent of its total area treated with additive depending on the 
treatment conditions used. Preferably, the discrete zone of filaments 
which have been treated with the smoke-modifying agent should constitute 
between 3 and 50 percent of the maximum cross-sectional area of the formed 
filter rod. It will be apparent to those skilled in the art that the 
cross-sectional shape of the discrete zone of treated filaments may be 
circular, elliptical, rectangular, etc. depending on the nozzle design 
used, the positioning thereof and the operating conditions used in 
manufacturing the filter rod. 
For a better understanding of this invention reference will now be made to 
the accompanying drawings. 
One embodiment of the present invention is shown in FIGS. 1, 2 and 3. 
Filter tow is processed in a conventional manner by withdrawing a 
continuous multifilament filter tow 11 from tow supply container 12 by 
feed rolls 16 and 17. The filter tow passes through pneumatic banding jet 
13 and over guide roll 14 before reaching feed rolls 16 and 17. Each side 
of the flattened band of filter tow is then contacted with wick-type 
applicators 20 and 21 where plasticizer is applied to the tow. The 
plasticized filter tow then proceeds through jet device 22 which loosens 
and blooms the filter tow by subjecting it to tension created by a rapidly 
moving stream of gas thereby producing a longitudinally oriented 
assemblage of filaments having individual filaments of the tow in 
substantial alignment. The bloomed filter tow 26 is withdrawn from the jet 
device by delivery rolls 24 and 25 and is directed to converging horn 27 
located adjacent to tongue device 28 associated with rod-forming means 55. 
A continuous paper web 52 from paper supply roll 50 passes over guide roll 
51 and into rod-forming means 55. Converging horn 27 gathers and 
compresses the longitudinally oriented assemblage of filaments 
transversely to the direction of filter tow movement and tongue device 28 
applies further converging and compressing action to the tow to produce a 
longitudinally oriented, compacted filter tow that can be enveloped by the 
paper web as the tow enters the rod-forming means. The longitudinally 
oriented and compacted filter tow, enveloped by the paper web, is 
temporarily confined in rod-forming means 55 by endless belt 54 which 
assumes a substantially cylindrical configuration as it passes through 
rod-forming means 55. The stable, continuous paper-wrapped filter rod 57 
is withdrawn from rod-forming means 55 by transport rolls 58 and 59 and is 
subsequently cut into sections 61 of desired length by cutting means 60. 
In addition to liquid plasticizer applied to the flattened band of filter 
tow by applicators 20 and 21, a liquid or vaporous additive is also 
applied to the filter tow as it moves through converging means just 
upstream of rod-forming means 55. This additive is injected into the 
interior portion of the gathered and compressed filter tow by conduit 
means 42 and nozzle means 43 (see FIGS. 2 and 3) concentrically positioned 
within the converging means so that the conduit means are in substantial 
longitudinal alignment with and enveloped in encircling fashion by the 
moving, gathered and compressed filter tow. Conduit means 42 is secured by 
support means 41. Preferably, conduit means 42 terminates in nozzle means 
43 (FIG. 2) which is designed to direct a radial spray pattern that is 
substantially perpendicular to the longitudinal axis of the moving filter 
tow. As shown in FIG. 3, nozzle means 43 may be conveniently fabricated 
from conduit means 42 by sealing off the terminus thereof with plug 45 and 
introducing a plurality of holes 46 circumferentially arranged around the 
periphery of conduit means 42 adjacent plug 45. Additive from additive 
supply tank 31 is fed by pump 32 through throttle valve 33 and conduit 34 
into conduit means 42 and nozzle means 43. The injection of liquid 
additive by nozzle means 43 is preferably accompanied by the injection of 
gaseous fluid to effect atomization of the liquid additive as it is 
injected into the filter tow. Thus, pressurized gas supply 38, throttle 
valve 39 and conduit 40 provide means for introducing a gaseous fluid into 
the liquid additive stream flowing through conduit 42. When a gaseous 
fluid is used to effect atomization, liquid additive is preferably 
introduced into the gaseous fluid stream by capillary tubing 35 (see FIG. 
7) positioned within T-joint 36. The use of capillary tubing 35 allows 
greater control over low flow rates of additive materials. 
Shown in FIG. 4 is another embodiment of the present invention which 
employs an alternative tow-processing arrangement. Those elements which 
are common to both FIG. 1 and FIG. 4 processing arrangements are given the 
same identifying numbers. In the FIG. 4 arrangement filter tow 11 passes 
through pneumatic banding devices 65 and 66 of known design which devices 
cause the tow to assume a flat band configuration. The flat band of filter 
tow is further widened and stretched longitudinally by spreading rolls 68 
and 69 which rotate at speeds in excess of the rotational speed of feed 
rolls 16 and 17. The flat, widened band of filter tow then passes through 
spray chamber 70 where plasticizer is applied to the filter tow. The 
plasticizer-treated filter tow 74 is then fed into stuffer jet device 76 
by delivery rolls 72 and 73. Each set of rolls 68 and 69 as well as 16 and 
17 preferably comprises one roll provided with circumferential grooves and 
one roll provided with a smooth surface of resilient or elastic material 
in order to promote more effective spreading, tensioning and transporting 
action. Circumferentially grooved rolls suitable for processing filter tow 
are described in U.S. Pat. No. 3,852,007 and may be adapted for use in 
connection with the present invention. The basic design of stuffer jet 
device 76 is disclosed in U.S. Pat. No. 3,050,430 and comprises a 
truncated cone-shaped device having a large end 79 (see FIG. 5) for 
receiving the filter tow, a small end 80 for discharging the filter tow 
and orifice means 81 intermediate the large end and small end through 
which a pressurized gaseous medium is introduced for moving the filter tow 
through the stuffer jet device. The pressurized gaseous medium is 
introduced into the jet device through tubular inlet 77. Concentrically 
positioned within the stuffer jet device 76 downstream of orifice means 81 
is nozzle means 78. Nozzle means 78 comprises a length of capillary tubing 
attached to conduit means 42 which is held in a fixed position by support 
means 41. Additive from supply tank 31 is introduced into conduit 42 in a 
manner similar to that described for the FIG. 1 apparatus. Stuffer jet 
device 76 acts as converging means for gathering and compressing the flat 
band of plasticizer-treated filter tow introduced into the large end 79 of 
the jet device. As the filter tow enters the small end 80 of the jet 
device it is subjected to a pressurized gaseous medium issuing from 
orifice 81 which promotes forward movement of the tow as the tow assumes a 
rope-like configuration. Simultaneously, additive emerging from nozzle 
means 78 is applied to the interior portion of the filter tow bundle. The 
additive may be injected with atomizing gas from pressurized gas supply 38 
or, alternatively, the additive may be injected without gas atomization by 
operating the apparatus with throttle valve 39 in the closed position. The 
treated tow is then further compressed by tongue device 28 in connection 
with enveloping the filter tow in a paper wrap and forming it into a 
stable, continuous paper-wrapped filter rod. When this tow processing 
arrangement is used, tongue device 28 is preferably provided with a 
plurality of small holes as shown in U.S. Pat. No. 3,050,430 to permit air 
directed into the tongue section by the stuffer jet to escape. 
The filter tow processing arrangement shown in FIG. 6 is similar to that 
depicted in FIG. 4 except that the nozzle means through which the additive 
is introduced is positioned within tongue device 28 as shown in FIG. 2 
instead of within the stuffer jet device 76. Also, the stuffer jet device 
76 as well as converging horn 27 are used to apply the gathering and 
compressing force to the advancing filter tow. 
Alternative nozzle arrangements are shown in FIGS. 10a and 10b for use in 
the tow processing apparatus depicted in FIGS. 1 and 6. FIG. 10a shows 
conduit means 42a and 42b terminating, respectively, in nozzle means 47 
and 48. Nozzle means 47 and 48 comprise lengths of capillary tubing 
extending longitudinally into the path of the filter tow and terminating 
at points below tongue device 28. Each of conduit means 42a and 42b may be 
supplied with a smoke-modifying agent from a single supply source to 
produce a filter rod having two zones of similarly treated filter tow. If 
desired, two separate supply sources may be used to supply different 
smoke-modifying agents to each of conduit means 42a and 42b to produce a 
filter rod having two different smoke-modifying agents applied to portions 
of the filter tow. 
In the arrangement shown in FIG. 10b, tongue device 28 is provided with an 
opening through which conduit means 42 is introduced. Conduit means 42 
extends into the inlet zone of rod-forming means 55 where it terminates in 
nozzle means 49. The portion of conduit means 42 which extends into the 
inlet zone of rod-forming means 55 is in substantial longitudinal 
alignment with the advancing filter tow 26. Hydraulic injection of the 
smoke-modifying agent by nozzle means 49 in the FIG. 10b arrangement is 
desirable. If the injection is carried out with gas atomization, the use 
of excessive gas pressures should be avoided so that the compacted filter 
tow is not disrupted by gas escaping from the confined tow in the 
garniture of the rod-forming means. 
Shown in FIG. 8 is a longitudinal cross section of a typical fibrous filter 
produced by the apparatus and method disclosed herein. A discrete zone 87 
of plasticized filaments treated with a smoke-modifying agent is 
circumferentially surrounded by a generally annular sheath 86 of 
plasticized filaments which have not been treated with the smoke-modifying 
agent. The entire bundle of filaments is enveloped by paper wrap 85. The 
end views of the filter shown in FIGS. 9a and 9b provide a good 
approximation of the radial distribution pattern that is obtained when 
additive is applied to the moving filter tow. The more limited 
distribution of additive in FIG. 9a results from a spray pattern that is 
directed primarily in the direction of the longitudinal axis of the filter 
tow whereas the distribution pattern shown in FIG. 9b results from a spray 
pattern that is substantially perpendicular to the longitudinal axis of 
the filter tow. Although the discrete zone 87 of treated filaments is 
shown in FIGS. 8, 9a and 9b as coinciding generally with the longitudinal 
axis of the filter rod, it is possible to position this zone adjacent to 
the outer periphery of the filter rod and paper wrap 85 as shown in FIG. 
9c by positioning the nozzle means near the periphery of the filter tow 
bundle. 
It is apparent that the presently disclosed invention is ideally suited to 
the introduction of flavoring materials into a filter rod because such 
materials are usually applied at very low levels. Pumps such as geared 
positive displacement pumps are capable of supplying precise, controlled 
amounts of additive materials at very low flow rates. Actual flow rates 
may be measured by commercially available devices such as flow meters 
based on mass flow or turbine flow principles. Continuous filter rods 
formed by the apparatus disclosed herein are characterized by very uniform 
longitudinal distribution of the applied additive. As noted previously, 
the transverse distribution pattern of the additive is determined by the 
position of the nozzle means with respect to the advancing tow, the design 
of the nozzle means and the particular operating conditions used. 
Generally, the additive applied to the filter tow in accordance with this 
invention is confined to a limited zone that coincides largely with the 
longitudinal axis of the filter rod when the nozzle means is aligned with 
that axis. It would, of course, be possible to position the nozzle means 
near the periphery of the bundle of filter tow so that distribution of the 
additive would occur in a peripheral zone of the formed filter rod. It is 
also apparent that two or more capillary tubes functioning as nozzle means 
can be positioned in the path of the advancing filter tow to obtain more 
complex distribution patterns in the formed filter rod. Separate additive 
supply systems for each capillary tube would afford a means for depositing 
two or more flavoring materials at transversely spaced locations in the 
formed filter rod. 
The apparatus disclosed herein would not ordinarily be used as the sole 
applicator of plasticizer to filter tow because normal operating 
conditions for this method and apparatus lead to treatment of only about 
75 percent of the tow as previously discussed. This apparatus could be 
used, however, to apply additional quantities of plasticizer to selected 
portions of the filter rod to modify the firmness characteristics of the 
formed filter rod. 
From the foregoing description, it is evident that this invention provides 
a convenient means for manufacturing a smoke filter comprising a 
plasticized, continuous multifilament filter tow formed into an elongated 
filter rod having individual filaments of the filter tow in substantial 
alignment with the longitudinal axis of the filter rod and wherein a 
selected portion of the filter tow is treated with a smoke-modifying agent 
to give a discrete elongated zone of treated filaments that is in 
substantial alignment with the longitudinal axis of the filter rod and 
substantially circumferentially surrounded by plasticized, continuous 
multifilament filter tow not treated with the smoke-modifying agent, the 
cross-sectional area of the discrete zone of treated filaments 
constituting between 1 and 75 percent of the maximum cross-sectional area 
of the formed filter rod. The formed filter rod is ideally suited to the 
manufacture of filter cigarettes using known methods for combining axially 
aligned rods of smokable material and filter rods. The filters may also be 
used in conjunction with other smoking products such as cigars, cigarillos 
and pipes. 
Although the preferred embodiments shown in the drawings include the 
application of a paper wrap to the filter tow, the basic arrangement shown 
could also be used in the manufacture of non-wrapped fibrous filter rods 
by employing rod-forming means provided with means for heating the filter 
tow. Apparatus for manufacturing non-wrapped fibrous filter rods is 
disclosed, for example, in U.S. Pat. No. 3,455,766 and British Pat. No. 
1,519,417 and such apparatus could be employed as the rod-forming means 55 
shown in FIGS. 1, 4 and 6. If flavoring materials are applied to filter 
tow being formed into non-wrapped filter rods, the distribution pattern of 
the flavoring materials in the formed filter rod may be somewhat more 
diffuse due to the heat that is applied to the filter tow in connection 
with the rod-forming operation and some loss of flavoring materials is 
also likely to occur due to the applied heat. This is particularly true 
when the filter tow is contacted with steam as it moves through the 
rod-forming means. 
EXAMPLE 1 
In order to demonstrate the effectiveness of the invention disclosed 
herein, commercially available filter rod-making apparatus was modified in 
a manner similar to that shown in FIG. 1. Stainless steel tubing having an 
inside diameter of approximately 1.6 mm was inserted through a hole in the 
wall of the converging funnel, the location of the hole being near the 
entrance end and on the lower side of the funnel. The tubing extended 
beyond the exit end of the converging funnel and terminated at a point 
near the entrance end of the tongue device (element 28 in FIG. 1). Solder 
was applied at the point where the tubing passed through the hole in the 
converging funnel in order to attach the tubing to the funnel and thereby 
maintain the termination point of the tubing in a relatively fixed 
position that was concentrically located and longitudinally aligned with 
respect to the filter tow entering the tongue section. The termination 
point of the tubing was sealed off by a plug of solder and a 25-millimeter 
section of the tubing adjacent to the plugged end was fashioned into 
nozzle means by providing it with ten 0.4-millimeter diameter holes 
uniformly spaced longitudinally and circumferentially to produce a radial 
spray pattern with respect to the longitudinal axis of the tubing. The 
open end of the stainless steel tubing was connected to one end of an 
aeration tee located a short distance from the converging funnel. The 
other end of the tee was connected to a source of compressed air (1550 
grams per square centimeter) and the side of the tee was connected to a 
liquid additive supply source. A solution of flavoring agents in triacetin 
was delivered to the aeration tee by a stainless steel positive flow gear 
pump that was mechanically interconnected with the drive motor of a filter 
rod-making machine by a toothed timing belt. A small quantity of red dye 
was also incorporated into the triacetin solution so that the distribution 
pattern and location of the applied additive could be visually observed in 
the formed filter rod. The filter rod-making machine was operated at a tow 
speed of 400 meters per minute using cellulose acetate filter tow while 
the triacetin solution was being injected into the moving tow via the 
concentrically positioned nozzle means at a rate of 150 milliliters per 
minute. A visual inspection of the resulting filter rod revealed a very 
uniform longitudinal as well as radial distribution of the applied 
additive. 
EXAMPLE 2 
The procedure of Example 1 was repeated except that the termination point 
of the stainless steel tubing was not sealed off and not provided with 
holes in the wall thereof. Thus, the aerated liquid additive was injected 
in a substantially longitudinal spray pattern rather than a radial spray 
pattern. The resulting filter rods were very similar to those obtained in 
Example 1 except that the radial distribution pattern was somewhat more 
concentrated (i.e., the cross-sectional area of the additive distribution 
pattern was smaller). 
While preferred embodiments of the present invention have been described 
above, it is apparent that additional modifications are possible without 
departing from the spirit and scope of the disclosed invention. Such 
modifications are deemed to fall within the scope of the appended claims.