Apparatus for detecting and/or controlling tension of a moving web, for example, a filamentary tow utilized in the production of cigarette filters

Apparatus for detecting and/or controlling tension of a moving web, for example, a filamentary tow, in a preselected zone of a longitudinal path traversed by the moving web. A sensing roller is journally supported by roller support structure, the latter having an opposing pair of deflection arms each of which is defined by edges which diverge from one another between inner supported and outer unsupported ends of the arms so that a region of reduced width (as measured in the general longitudinal direction of the web) is provided near each inner supported end. A reaction force which is indicative of the web's tension will thus be exerted against the sensing roller and transferred to the roller support structure so as to responsively cause the deflection arms to be resiliently flexed in the general direction of the reaction force. The extent of such resilient flexion is detected with strain gauges operatively connected to the deflection arms and output a signal indicative of the web's tension to provide monitoring and/or control thereof.

FIELD OF INVENTION 
The present invention relates to the field of tension detecting and/or 
controlling apparatus. More particularly, the invention herein described 
and claimed relates to apparatus which detect and/or control tension of a 
moving web, for example, a filamentary tow utilized in the production of 
cigarette filters. 
BACKGROUND OF THE INVENTION 
Cigarette filters have conventionally been produced from longitudinally 
extended crimped filaments bonded to one another at their contact points 
by solvation bonds. The procedure for producing such filters involves 
producing a tow (or several thousand continuous filaments), crimping the 
tow, opening the tow to deregister adjacent crimps, uniformly applying a 
plasticizer to the opened tow, fluffing the tow, and thereafter condensing 
the plasticized tow to reduce its cross-sectional size until it is 
approximately equal to the cross-sectional size of a cigarette. The 
condensed mass is formed into a coherent structure, typically by wrapping 
paper around it and severing the wrapped tow into rods of predetermined 
length. The rods are thereafter cured to effect bonding between adjacent 
filaments at their contact points. 
Because of the expense of the tow component of cigarette filters, it is 
desirable that the greatest amount of tow bulk be attained per unit weight 
of filamentary material. One method of expanding the tow in which the 
present invention is particularly well suited for use is described in U.S. 
Pat. No. 3,099,594 (the entire disclosure thereof being expressly 
incorporated hereinto by reference) wherein crimped continuous tow is fed 
into a jet supplied with high velocity gas whereby the crimps in the 
filaments are deregistered. More specifically, in the process of U.S. Pat. 
No. 3,099,594, a continuous multifilament crimped tow is withdrawn from a 
supply bale by means of a feed roll pair and passed by the suction of a 
blooming jet over a suitable plasticizer applicator into the blooming jet. 
In the blooming jet, the tow is subjected to an explosive expansion of 
compressed air so as to cause blooming or fluffing of the tow. The bloomed 
tow is then expelled from the jet under the influence of the expanding air 
flow into a filter rod-making machine whereby the tow is condensed into 
rod-like form as previously discussed. 
The tow is also sometimes subjected to longitudinal tension upstream of the 
blooming jet according to the methods disclosed in, for example, U.S. Pat. 
Nos. 2,790,208 and 2,926,392, which are each incorporated hereinto by 
reference. According to the methods described in these patents, the 
longitudinally moving tow is generally subjected to continuous 
longitudinal tension in a zone established between a pair of tension rolls 
and a pair of retarded rolls (sometimes called "feed rolls" and 
"pretension rolls", respectively, in art parlance). The feed rolls are 
driven at a speed greater than the pretension rolls so that the tow is 
subjected in the zone therebetween to continuous longitudinal tension. 
Upon emerging on the downstream side of the feed rolls, the applied 
tension is suddenly released to thereby allow the crimped tow to relax. 
Such applied tension and then sudden relaxation assist in opening the tow 
prior to treatment by the blooming jet. 
However, the tension applied in the tension zone by means of the feed and 
pretension roll pairs may not be uniform once an operator has set the 
tension in the zone for a given tow product. Such nonuniformity of applied 
tension may therefore be manifested in variability of the resulting filter 
rod characteristics, for example, pressure drop per unit rod weight, from 
one rod to another thereby leading to a nonuniform filter rod product. 
SUMMARY OF THE PRESENT INVENTION 
It is one object of the present invention to provide apparatus for 
detecting the tension of a moving filamentary tow so that variations in 
the tension thereof may be monitored and/or controlled so as to reduce 
rod-to-rod variabilities, such as pressure drop variabilities per unit rod 
weight. A further object of this invention is to provide apparatus which 
can be moved into and out of contact with the moving filamentary tow so 
that the tension of the tow can either be periodically detected at 
preselected intervals or continuously detected during processing of the 
tow into cigarette filter rods. 
These and other objects (which will become more clear to the reader after 
consideration of the detailed description thereof which follows) are 
achieved by means of apparatus having a sensing roller which is rotatable 
about its central axis and a roller support which supports the sensing 
roller in a generally transverse relationship to a longitudinal path 
traversed by a moving web or tow. The tow thus contacts the sensing roller 
and exerts a force thereagainst which is indicative of the tension of the 
tow. The roller support includes an elongate bottom support plate disposed 
parallel to the central axis of the sensing roller and thus is also 
positioned transverse to the tow's longitudinal path. The bottom support 
plate includes a central region and a pair of opposing arms each having an 
inner end (preferably integrally joined to the central region) and an 
outer, unsupported end spaced from the inner end in a transverse direction 
relative to the tow's longitudinal path. Each of the arms have an opposing 
pair of sides which outwardly diverge from one another along the 
transverse direction between the inner and outer ends such that a reduced 
width dimension is present near the inner end of each arm as compared to a 
width dimension near the outer end thereof. 
A pair of spaced-apart journal supports are fixed to and upstandingly 
extend from respective ones of the outer, unsupported ends of the support 
arms so as to journally mount the sensing roller therebetween for 
rotational movement about its central axis. The journal supports also 
transfer the force exerted upon the sensing roller to the unsupported ends 
of the bottom support plate. Such transferred force thereby causes the 
arms to be resiliently flexed in the direction of the transferred force 
and the extent of flexion is detected by suitable means which, in a 
preferred embodiment, is comprised of strain gauges connected in a 
Wheatstone Bridge arrangement. The output from the strain gauges can thus 
be coupled to monitoring equipment and/or utilized to regulate the 
longitudinal tension applied to the tow.

DETAILED DESCRIPTION OF THE PREFERRED EXEMPLARY EMBODIMENTS 
A cigarette filter rod making apparatus 10 with which the tension detecting 
device 12 of this invention is particularly well suited for use is shown 
schematically in accompanying FIG. 1. As can be seen, a filamentary tow 14 
is removed from a supply bale 16 and passes through a pneumatic banding 
jet 18 which initially spreads the tow laterally to thereby provide 
preliminary opening of the tow. The tow 14 then passes over idler roll 20 
and is directed to the nip formed between pretension roll pair 22, 24. 
Driven feed roll pair 26, 28 is located downstream of pretension roll pair 
22, 24. A tensioning zone 30 is defined between pretension and feed roll 
pairs 22, 24 and 26, 28, respectively. Longitudinal tension is thus 
applied to the tow band 14 in zone 30 by means of pretension roll pair 22, 
24 and feed roll pair 26, 28, for example, in accordance with the 
techniques disclosed in U.S. Pat. Nos. 2,797,208 and 2,926,392. The 
longitudinal tension applied in zone 30 is suddenly released immediately 
downstream of feed roll pair 26, 28 so as to assist in the partial opening 
and deregistration of crimps in the tow band 14. The thus partially opened 
tow band (now designated by numeral 31) is then passed over plasticizer 
wick applicators 32a, 32b which together uniformly apply a plasticizing 
liquid onto the tow band 31. The plasticized and partially opened tow 31 
is then fed into a blooming jet 34 so as to significantly fluff or 
completely bloom the tow 31 by means of a pressurized fluid, e.g., air. 
The flow air exiting blooming jet 34 feeds the bloomed tow (now designated 
by numeral 35) between a pair of delivery rolls 36a, 36b which serve to 
preliminarily compact the tow into rope-like form and control the delivery 
of the preliminarily compacted tow (now designated by reference numeral 
37) to garniture 38 where further compacting of the tow 37 occurs. A 
srapping paper 40 is also concurrently fed into garniture 38 so that as 
the tow 37 is further compacted into rod-like shape by means of garniture 
38, paper 40 will be wrapped therearound to produce cigarette rod element 
42. Rod element 42 may then be cut by means not shown into convenient 
lengths for attachment to a tobacco column. 
As seen in FIGS. 2-4 the tension detecting device 12 of this invention 
generally includes a sensing roller 50 supported by roller support 
structure 52 (see FIG. 3) so that the sensing roller 50 contacts the tow 
band 14 in zone 30. The roller support structure 52 includes a planar 
bottom support plate 54 having a pair of deflection arms 56, 58 integrally 
joined to one another at their respective inner ends 57, 59 to form a 
central region 60 (see FIG. 4). As shown in FIG. 4, each deflection arm 56 
and 58 has leading and trailing edges 56a, 56b and 58a, 58b, respectively, 
which outwardly diverge from one another between the inner ends 57, 59 and 
the outer, unsupported ends 61, 63, respectively. Thus, the width 
dimension of each arm 56 and 58 (as measured in the longitudinal direction 
of tow movement) is less at the inner ends 57, 59 as compared to the width 
dimension of arms 56, 58 at their respective outer, unsupported ends 61, 
63. Moreover, the width dimension of central region 60 is similarly of a 
reduced width dimension as compared to the width dimension of the outer 
ends 61, 63. As exemplary dimensions, support plate 54 may be 10 inches 
long (as measured transverse to the longitudinal direction of tow 
movement) with central region 60 and outer ends 61, 63 being 1/2 inch and 
13/8 inches wide, respectively. 
The outer ends 61, 63 of deflection arms 56, 58, include journal support 
members 66, 68, respectively. Journal support members 66, 68 are provided 
with bearings 70, 72, respectively, so as to mount sensing roller 50 for 
rotational movement about its central axis 74. 
The central region 60 of support plate 54 is rigidly coupled to an upper 
end 79 of support post 80 by means of bolts 81 as may be seen more clearly 
in FIG. 3. Support post 80 includes a sleeve 82 which is slideably coupled 
to transverse support 84, the latter being dependently supported from 
frame 87 (see FIG. 2) of apparatus 10 by means of a bracket member 89 
fixed to each end of rod 84. Sleeve 82 permits pivotal movements of the 
support post 80 (and thus the sensing roller 50) between an operative 
position wherein the sensing roller 50 is in sensing contact with the tow 
band 14 (as shown in solid line in FIG. 2) and an inoperative position 
wherein the sensing roller 50 is spaced from the tow band 14 (as shown in 
phantom line in FIG. 3). 
The tail end 85 of support post 80 carries a magnet latch member 86 which 
contacts strike plate 88 when the support post 80 is in its operative 
position thereby to maintain the sensing roller 50 in operative sensing 
contact with tow band 14. A pair of lateral stops 90, 92 are provided on 
each side of sleeve 82 so as to prevent lateral slippage and/or 
displacement of support post 80 upon transverse support rod 84. 
Additionally, a pair of stop members 94, 96 having limit flanges 94a, 96a, 
respectively, are provided so as to be in registry with unsupported ends 
61, 63 so that the unsupported ends 61, 63 will bear against flanges 94a, 
96a when support post 80 is in its inoperative position. Flanges 94a, 96a 
thereby establish the inoperative position of support post 80. Tail end 85 
of support post 80 also defines a smooth, preferably planar, surface 97 so 
that tow band 14 may slide therealong without substantial drag being 
imparted thereto when support post 80 is in the inoperative position (see 
phantom line showing thereof in FIG. 2). 
Paired strain gauges R.sub.1 -R.sub.4 are operatively bonded to respective 
upper and lower surfaces of central region 60 of bottom support plate 54 
laterally of center support post 80 as is schematically shown in FIG. 3. 
Strain gauges R.sub.1 -R.sub.4 are of the conventional type, for example, 
Model No. CEA-13-250UW-350 available from the Micro-Measurements Division, 
Measurements Group, Inc. of Raleigh, N.C., and are connected to one 
another in a Wheatstone Bridge arrangement as shown in FIG. 5. As is seen 
therein, the outputs of the strain gauges R.sub.1 -R.sub.4 of the bridge 
are fed into, for example, an amplifier 98 of conventional construction so 
as to amplify the output signals, for example, in the range of 0-5 volts 
which is proportional to the sensed tension of tow 14. The amplified 
output signal is then filtered by filter 99 to remove "noise" therefrom, 
such as machine vibrations. The thus filtered signal may then be sent to a 
suitable indicator 100 (see FIG. 1) to provide a human-readable indication 
of the tension of tow band 14 in zone 30. 
The filtered signal emanating from filter 99 may, alternately or 
concurrently, be utilized to control the tension of tow 14 within zone 30. 
For example, the signal may be fed into control unit 104 (see FIG. 5) 
which determines whether or not the tension of tow 14 in zone 30 is 
greater than or less than a tension setpoint. If a high or low tension 
limit is determined, control unit 104 will then issue a command signal to 
drive means 106 which is operatively coupled to pretension rolls 22, 24 so 
as to cause pretension rolls 22, 24 to either drive at greater or lesser 
rotational speed to respectively cause the tension of tow 14 in zone 30 to 
decrease or increase until the tension setpoint is again achieved. Drive 
means 106 may also take the form of an electric or pneumatic actuator 
which displaces one of the pretension rolls 22, 24 relative to the other 
to adjust the nip pressure exerted thereby upon tow 14 thus selectively 
varying the tension of tow 14 in zone 30. 
In operation, the tension detecting apparatus 12 of this invention is 
pivoted into its operative position either manually or via suitable 
electronic or pneumatic actuator noted generally in FIG. 1 by reference 
numeral 102. While in the operative position, the tow band 14 will be 
deflected upwardly so that a force "F" (see FIGS. 2 and 3) which is 
indicative of the tension of tow band 14, will be exerted against sensing 
roller 50. Force "F" will then be transferred via journal supports 66, 68 
to the outer, unsupported ends 61, 63 of amrs 56, 58, respectively. The 
force transferred to the outer, unsupported ends 61, 63 will thus 
downwardly displace (i.e., in the direction of force "F") the ends 61, 63 
which, in turn, causes the bottom support plate 54 to be downwardly bowed 
or flexed laterally of support post 80 as is schematically shown by dashed 
line in FIG. 3. Owing to the reduced width of central region 60 near inner 
ends 57, 59 of arms 56, 58, respectively, the resilient flexion of bottom 
support 54 will be more pronounced thereat so as to facilitate detection 
of the extent of flexion by means of strain gauges R.sub.1 -R.sub.4. 
Variations of the tension of tow band 14 in zone 30 will thus be 
manifested by variations of magnitude of force "F" which will, in turn, be 
detected by strain gauges R.sub.1 -R.sub.4 as previously described and 
converted to human-readable form by means of indicator 100, and/or 
utilized to selectively control the speed of pretension rolls 22, 24, and 
thus the tension of tow 14 in zone 30, for example. 
As may be appreciated, since flexion of both arms 56, 58 is being detected 
by strain gauges R.sub.1 -R.sub.4, the apparatus 12 is insensitive to the 
location of tow band 14 along sensing roller 50. That is, should the tow 
shift laterally along roller 50, towards, for example, journal support 66, 
deflection arm 58 associated with the other journal support 68 will be 
downwardly flexed to a lesser extent than deflection arm 56 associated 
with journal support 66. Deflection arm 56 associated with journal support 
66 will however be downwardly flexed to a correspondingly greater degree 
as compared to arm 58. The output signals emanating from the Wheatstone 
Bridge arrangement of strain gauges R.sub.1 -R.sub.4 (see FIG. 5) will 
thus not exhibit a net decrease or increase in the extent of flexion of 
bottom support 54. 
The shape of sensing roller 50 however is such that lateral tow shifting 
therealong is minimized. As seen in FIG. 3, sensing roller 50 has 
generally a concave shape defined by means of a central cylindrical 
portion 50a and laterally opposing truncated cone portions 50b, 50c each 
having their truncated apex joined to central portion 50a. Thus, should 
tow band 14 laterally shift away from central portion 50a, the laterally 
divergent cone portions 50b or 50c will urge the tow band 14 back towards 
central portion 50a. The particular generally concave shape of sensing 
roller 50 and the "balanced" arrangement of strain gauges R.sub.1 -R.sub.4 
thereby ensures that the output signals issuing therefrom will be 
substantially free from deviations which may otherwise occur should tow 
band 14 shift laterally upon roller 50. 
While the present invention has been herein described in what is presently 
conceived to be the most preferred embodiment thereof, those in this art 
may recognize that many modifications may be made thereto, which 
modifications shall be accorded the broadest scope of the appended claims 
so as to encompass all equivalent apparatus, devices or structures.