Cigarette filter rod minimum point gauge

Provided is an apparatus which allows for the facile and accurate measurement of the recess of a cylindrical core of filter tow which is surrounded by a paper wrapper which extends beyond the core to form the recess.

FIELD OF THE INVENTION 
This invention is directed to a method and device for determining the 
capability curve minimum point of cellulose acetate filter rods. 
BACKGROUND OF THE INVENTION 
Cellulose acetate fibers are widely used as filters for various tobacco 
products, e.g., cigarettes. The fibers themselves are often referred to as 
"filter tow" and are generally produced by forcing an acetone/cellulose 
acetate dope through a spinnerette under pressure sufficient to form a 
continuous bundle of fiber, which is subsequently compacted to form a 
filter rod. 
One of the primary methods for determining the filtration performance range 
for a given sample of filter tow is the calculation of the so-called 
"capability curve". A capability curve's minimum point can be consistently 
determined if care is taken by the plugmaker operator to obtain filter rod 
recess which is indicative of a minimum point. A plugmaker operator can 
often repeatedly adjust to the same amount of recess which he feels 
represents a minimum point. However, a different operator may get a 
significantly different amount of recess which he felt represented the 
same minimum point and neither one may repeatedly have obtained the 
desired amount of recess. While apparent recess differences may appear to 
be small, the pressure drop of the filter rods can be markedly different. 
Specific properties of filter rods are affected by the properties of the 
tow used to make the rods and by other rod properties. 
A capability range of filter rod weight and pressure drop is possible with 
cellulose acetate filter tow because crimped tow is extensible. The 
relationship between the weight of tow in a filter rod and the pressure 
drop of the rod is direct and linear for a given tow sample. As the speed 
of the tow processing unit is increased or decreased in relation to the 
speed of the plugmaker, there will be a corresponding increase in rod 
pressure drop. 
To determine the capability range of a given tow item on a specific 
filtermaking machine, filter rods should be produced at the highest tow 
weight possible (i.e., maximum capability) and the lowest weight possible 
(minimum capability). The maximum capability point is normally defined as 
the point at which the garniture of the plugmaker will not accept 
additional tow. Attempts to increase the tow weight beyond this point will 
result in roll wraps, failure to seal the rod seam, or excessive variation 
in filter rod properties. The minimum capability point is normally defined 
as supplying the lowest tow weight possible to the garniture while 
maintaining an acceptable rod from the standpoint of no wrinkles and very 
slight end recess (approximately 1.0 mm). In capability evaluations, rods 
at midpoint weight (halfway between minimum and maximum) are also 
produced. The rods produced at these three conditions (maximum, minimum, 
and midpoint) are tested from circumference, weight, and pressure drop and 
the results are plotted graphically. When a line is drawn through these 
plotted points, the pressure drop/weight relationship can be determined at 
any point along the line. The line generated by this procedure is 
generally referred to as a "capability curve", see FIG. 4. 
An important point to remember regarding the "capability" of a tow item on 
a particular type of filter making equipment concerns target placement. If 
the target is not well placed on the capability curve, it is likely that 
processing difficulties or poor quality rods may result. If the above 
parameters are used for the determination of the minimum capability point 
(rod recess approximately 1.0 mm and no wrinkles), selection of a target 
pressure drop of at least 15 percent above the minimum pressure drop is 
preferred. If slow speed filter making equipment is used or if standard 
tow transport jet systems are used on high speed filter makers, the target 
pressure drop should not be more than 25 percent above the minimum 
pressure drop. If "capability extension" systems such as the EASTMAN Type 
II tow transport jet or the modified HAUNI tow transport jet system are 
used, the upper limit for target pressure drop may be increased to as much 
as 50 percent above the minimum pressure drop. In this fashion, target 
pressure drop is referenced to the minimum point.

SUMMARY OF THE INVENTION 
The present invention provides an apparatus which allows for the facile and 
accurate measurement of the recess of a cylindrical core of filter tow 
which is surrounded by a paper wrapper which extends beyond the core to 
form said recess. In the use of the apparatus of the present invention, 
the end of the filter rod is illuminated, at a proper angle, to allow the 
recess to be measured through a magnifier and scale (mm) arrangement. By 
the use of this apparatus, rod recess can be measured to the nearest 0.125 
mm. 
DETAILED DESCRIPTION OF THE INVENTION 
This invention provides an optical means for a plugmaker operator to 
quickly and accurately measure a filter rod's recess by combining the two 
presently used methods, i.e., the microscopic analysis and the visual 
estimate. The present invention is more accurate than the visual estimate, 
and yet is more conveniently done than the microscopic analysis. 
In a preferred embodiment of the present invention, the body (10) of the 
apparatus, which requires some drilling and machining, can be fabricated 
from any durable material, for example MYCARTA.TM.. The body accommodates 
a light source (15), a switch (11), a turret (12) having a multiplicity of 
variable-sized circular openings (23), an eyepiece (13), and associated 
retaining hardware. The turret may be fabricated from the same material as 
the body. The turret (12), is rotatably mounted on the apparatus via the 
rotation of the attached barrel (25). The barrel (25) preferably has at 
least one locating pin and ball (27) which engage a groove (26) on the 
barrel (25). 
The light intensity from the light source (15) must be of sufficient 
intensity to easily read the scale (18) above the illuminated paper/tow 
interface, but should not be so bright as to "wash out" the identification 
of the paper/tow interface or recess (19). The light illumination angle 
(21) is not critical and need only allow illumination at the filter rod's 
end at the plugwrap paper/tow interface. 
The light source may be provided by a reflection of ambient light or by a 
battery-operated light (e.g., (24)) or AC-powered light of conventional 
construction. In a preferred embodiment of the present invention, the 
light source is a battery-operated light. In either case, the light source 
is preferably controlled by a switching means (11). Said switching means 
may be momentary-on type switch which would provide a light source for the 
time necessary to make the visual inspection of the minimum point. 
Alternatively, the switching means may be a microswitch (17) located in 
the rod barrel (22) which would engage said light source (11) when a 
filter rod is inserted. 
Operation of the Device 
One end of a filter rod (14) is partially inserted into the lowest usable 
diameter turret hole (23). The operator then looks into the eyepiece, 
turns on the light, and completes the insertion until the end of the paper 
coincides with the "0" mm mark on the engraved reticle (18). The filter 
rod is then rotated, keeping its end aligned with the "0" mm mark, until 
the area of greatest average tow recess is observed and the recess amount 
is read from the scale. Although the scale is divided into 0.25 mm 
increments, it is possible to determine recess to the nearest 0.125 mm. 
After removing the filter rod, it is preferred that the additional filter 
rods be tested for a statistically significant number of times to 
calculate an average recess for the filter rods in a lot. 
The device of the present invention has been routinely used to determine 
the minimum points of capabilities performed on a variety of tow types. 
After giving plugmaker operators a specific recess in millimeters which 
has been defined as an acceptable minimum point, there has been a definite 
improvement in the plugmaker operator's ability to obtain consistent 
minimum points, particularly when performing multiple capability tests on 
the same tow type. As with any instrument which requires an individual's 
visual assessment, even when given a scale to use, there remains some 
degree of interpretation. However, the range of interpretation has been 
greatly reduced by the present invention. Since filter rods are by their 
very nature somewhat fragile, care must be taken when handling the rods 
and inserting them into the device. 
There is currently no device which will easily assist a plugmaker operator 
in determining when a capability minimum point is reached. In most cases, 
this analysis is a very subjective assessment, and the results can be 
quite variable when the capability minimum points of several different 
plugmaker operators are compared for the same filter tow type. This 
invention provides the means to more accurately and consistently obtain a 
capability minimum point not only for one plugmaker operator, but also 
among many plugmaker operators. 
Thus, the present invention provides an apparatus for measuring the recess 
of a filter rod wherein a generally cylindrical core of filter tow is 
surrounded by a translucent wrapper which extends beyond said core to form 
a recess of the core, comprising 
(a) a support for holding a filter rod in a fixed position; 
(b) a light source or means for reflecting ambient light, said light source 
having sufficient intensity at the end of said filter rod, to allow for 
optically showing the extent of said recess; and 
(c) a scale adjacent said filter rod at the recess thereof whereby the 
recess can be measured by the extent of the illuminated wrapper.