Method for continuously measuring the perimeter of wrapped objects of generally uniform cross-section

Disclosed is a method of continuously determining the perimeter of an elongated object of generally uniform cross-section which comprises wrapping the object with a sheet of flexible material having a single band imprinted thereon in such manner that the single band extends axially parallel to the object and becomes partially obscured by an overlapping edge of the sheet, placing detection means in position to detect the width of the unobscured portion of the single band, the detection means being capable of determining the width of the unobscured portion of the single band, moving the object and the detection means relative to each other in a manner such that continuous detection of the single band and the measurement of the width of the unobscured portion of the single band occurs and correlating the measured width of the unobscured portion of the band to the perimeter of the object.

TECHNICAL FIELD 
This invention relates to a method for continuously monitoring the 
peripheral measurement of wrapped objects. It has particular utility in 
instances where an object is wrapped with sheet material, such as in the 
case of cigarette filters, where a bundle of fibers is wrapped with paper. 
BACKGROUND ART 
Earlier methods of determining the diameter or circumference of a cigarette 
filter plug have utilized an air gauge device which requires that the plug 
be encircled by a pressurized annulus which is arranged to measure the 
amount of air escaping from the annular gap between the outer 
circumference of the filter plug and the inner diameter of the annulus. 
Such a device is operable as long as the circumference wrap of the filter 
plug is airtight. Such an arrangement permits pressure to build up due to 
the narrowness of the annular gap between the encircling annulus and the 
filter rod. If air is permitted to escape via means other than the gap, 
the measuring system is not accurate. This is the case when the paper 
forming the outer surface of the filter rod is porous. With the advent and 
need for a porous outer wrap for the filter plug rather than the 
relatively airtight wrap used in earlier versions of the filter plug, 
improved means of measuring the diameter of the filter plug are required. 
These means must be unaffected by porosity of the filter plug wrapping 
paper. 
In the manufacture of cigarette filter plugs, it becomes necessary to 
assure that the diameter or circumference of the wrapped plug conforms to 
the dimensions of the subsequent cigarette resulting from the assembly of 
the filter plug with the cigarette. 
In our copending U.S. patent application Ser. No. 409,754, filed Aug. 19, 
1982, we disclosed a process of measuring the circumference of the filter 
plug in which two or more lines running in a direction parallel to the 
long dimension of the paper are imprinted on the filter wrap paper. Since 
the paper is wrapped around the filter plug core fibers so that the long 
aspect of the paper runs parallel with the filter plug axis, these lines 
then run longitudinally along the filter rod. By positioning the lines so 
that they fall near the overlap where the seam is made in the filter rod 
wrapper as it surrounds the core fiber bundle, means are offered to 
reference a dimensional measuring system. By determining the separation of 
the lines positioned on either side of the overlapped seam it is possible 
to determine the circumference of the filter rod, since the lines are 
placed a known distance apart and the circumference is composed of this 
known distance plus the measured distance between the lines as they appear 
separated by the overlapped seam. Through the use of video measuring 
apparatus such as a standard television camera or a linear array 
solid-state video measuring device, the spacing between the two lines 
separated by the seam can be accurately determined. If four lines are 
imprinted, the measurement between the outer lines and the inner lines can 
be used to determine the extent of stretching of the paper thereby 
offering a means of accurately compensating for the stretch of the paper 
in the measurement of the filter rod circumference. Should electronic 
means not be acceptable, an optical measuring device consisting of either 
a magnifying lens with incorporated reticle or a projection screen device 
incorporating a scale for measurement may be used. 
We have since discovered that a greater simplification may be achieved in 
the printing of the dimensional establishing elements on the filter wrap 
material. This simplification is such that only one band of contrasting 
color or black may be printed on the wrapping material. The result of this 
discovery is that the production process is simplified for making the 
gravure roll required to print the wrapper by the gravure process, or 
making plates or letterpress type to print the wrapper by either the 
lithographic or letterpress process may be simplified. The nature of our 
discovery is such that it was unanticipated in our previous disclosure. In 
our copending process, which was devised around the concept of printing 
two lines of identical width but spaced to be equidistant from the edges 
of the filter wrapping material, the process required that the two color 
stripes or bands be precisely positioned and spaced on the wrapper 
material. Control of both the width of each band and the spacing between 
bands must be precise, and this is made difficult by the tendency of the 
inks used in the gravure process to spread, and the tendency of 
letterpress and lithographic inks to form an indistinct edge. In the 
process of the present invention, we provide an improvement in precision 
because of the eliminations of three printed edges and the necessity for 
spacing two bands a specified distance apart. 
DESCRIPTION OF THE INVENTION 
According to the present invention, therefore, we provide a method of 
continuously determining the perimeter of an elongated object of generally 
uniform cross-section. The process comprises 
a. forming on a flexible elongated sheet a single band of predetermined 
width and of contrasting color with respect to the sheet, the band being 
parallel to two opposite elongated and parallel edges of the sheet, and 
wrapping the elongated object with the sheet so that one of the opposite 
elongated edges is overwrapped with respect to the other of the elongated 
edges and overlies and obscures a portion of the width of the single band, 
the single band being generally axially parallel to the elongated object; 
b. placing detection apparatus in position to detect the single band on the 
elongated object, the detection apparatus having an arrangement for 
determining the width of the unobscured portion of the single band; 
c. moving the elongated object and the detection apparatus relative to each 
other in a manner such the continuous detection of the width of the 
unobscured portion of the single band occurs; and 
d. correlating the measured width to the perimeter of the elongated object. 
The single band may be printed with an optically detectable ink. 
The detection apparatus in the method may be a line array video camera 
which is capable of receiving reflected light on an arrangement of 
photoelectric sensor elements connected in a manner such that the position 
of displacement of the reflected light form a predetermined position on 
the arrangement is sensed electronically by counting the number of 
photoelectic sensor elements between the aforementioned predetermined and 
displacement positions. 
The method may also comprise the step of adjusting the perimeter of the 
object in response to detection of a change in the width of the unobscured 
portion of the single band. 
The method further may include the steps of generating an electrical signal 
which is proportional to the number of sensor elements counted, using the 
aforementioned electrical signal to measure the width of the unobscured 
portion of the single band, and correlating the measured width to the 
perimeter of the object. 
The elongated object of the method may be a cigarette filter rod. 
This project has specific utility in the manufacture of cigarette filter 
rods in which a fibrous core of material is wrapped in a porous paper 
wrapper. It has utility also in the diameter control of those tubular 
elements which in combination form the structure of a cigarette. Although 
it will be apparent to those skilled in the art that the method disclosed 
herein is useful in many other fields where perimeter measurements must be 
continuously monitored, for the sake of simplicity the method will be 
described herein with respect to cigarette filter rods. 
The process and apparatus described can be used in any manufacturing 
process where webs of elongated flat material are converted into tubing by 
rolling the flat material around the longitudinal axis of the web. In the 
manufacture of cigarette filter plugs, web material is rolled into a tube 
to form the wrapper for fibrous filter material which serves as the core 
of the filter. In the manufacture of tubing from paper, plastic, fabric, 
glass, etc., where a flat web is rolled from a tubing by lapping over the 
edges of the web material and sealing the edges together, the placement of 
a single band of contrasting color along the back side of the web material 
will permit automatic control of the circumference and thus the diameter 
of the tubing. 
The means by which such a circumferential determination can be made from 
the filter plug is based on the placement of a single band of 
predetermined width and contrasting color on the wrapper paper. The single 
band runs along the wrapper paper parallel to the edges of the paper as it 
is withdrawn from the paper roll. The paper is folded into an elongated 
cylinder which encloses the fiber filter plug core. Thus the single band 
imprinted on the paper will be parallel to the long dimension of the paper 
and will also be parallel to the axis of the filter plug. By arranging the 
single band so that it is either near to or borders one of the 
longitudinal edges of the filter rod wrapper, it is possible to determine 
the circumference of the filter rod simply by measuring the unobscured 
width of the single band after it has been rolled around the filter 
material so that one of the longitudinal edges of the wrapping paper 
overlaps the opposite longitudinal edge and a portion of the single band 
imprinted on such wrapping paper.

BEST MODE FOR CARRYING OUT THE INVENTION 
As will be noted from FIG. 1, the paper 10 is flat and elongated prior to 
being wrapped around the fibrous core material of the filter plug 12. At 
point 14, the paper is caused to roll and gradually close until at point 
16 using conventional equipment well known to those skilled in the art, it 
has become a cylinder with a seam formed by overlapping the paper where it 
is joined by an adhesive strip. 
Single band 18 is parallel with and approximately aligned with the edges of 
the paper. The single band 18 is imprinted on the paper and becomes 
partially obscured by the overlapping paper, as may be seen from other 
edge 19 of the single band shown in dotted lines. The unobscured portion 
or width of the single band is shown at 22, which is bordered by the edge 
of the overlapping portion of the paper. 
Electronic means 24 are provided for measuring the unobscured width of the 
single band 18. The electronic means or line array video camera 24, such 
as manufactured by the Reticon Corporation of Sunnyvale, Calif., is 
positioned above the continuous filter rod prior to the filter rod being 
segmented into individual filter elements or plugs. The electronic output 
of the array video camera can be appropriately processed and used to 
readjust the controls which affect the circumference of the filter rod 25. 
Thus, the filter rod diameter control can be fully automatic. 
Should automatic control of filter rod diameter not be required, an 
alternate process employs a projection lens and screen (not shown). The 
image of the single band greatly magnified is projected on a screen. This 
is compared to a built-in scale imposed on the screen and the operator 
judges the degree of adjustment needed to bring the single band within 
control limits. When the single band is appropriately adjusted to the 
proper width, the process is in control. 
In a fully automated system incorporating the video camera 24 using either 
a linear array of photocells or a full video tube camera, the arrangement 
is as shown in FIG. 3. Here the filter rod 25 is imaged on the sensitive 
medium of the video camera 24. The video signal is sent to signal 
processor 26 where it is compared with the desired band width information. 
An error signal may be sent from this processing unit to the electrical 
signal-to-mechanical signal translator 28 where it may be translated into 
either a pneumatic, hydraulic, or electrical signal which is supplied to 
the control element 29, which is an adjustable trumpet folder for 
adjusting the filter rod circumference. FIG. 1 illustrates in diagrammatic 
form how to adjust the perimeter of the rod by moving adjustable trumpet 
folder 29 with respect to stationary trumpet folder 31. The curvature 
details are not shown for the trumpet folders, but they are well known to 
those skilled in the art. 
Use of the line array video camera 24 such as illustrated in FIGS. 3-5 
(well known in the art and commercially available) as a means of measuring 
the unobscured width 22 of the single band 18 on the wrapper paper 10 is 
based on the construction of the linear photosensor array in the camera. 
The principal of operation of such a camera is illustrated in FIGS. 4 and 
5. The camera focuses the reflected rays of light 36, 38, 40, and 42, by 
means of lens 30, onto a plate 32 having a plurality of photoelectric 
sensor bars 34, which are activated to generate an electrical signal 
proportional to the distance between the first bar illuminated, or the 
last bar left dark, and the beginning of the photoelectric sensor array. 
The camera and image source are aligned so that the furthermost level to 
be determined as to distance by the system produces light source which 
falls upon the first photoelectric sensor in the array. The distance 
between this first sensor and the other sensors in the array is then 
determined by counting the number of pulses which must be applied to the 
array in order to effect stepping from one photosensor to another, thus 
effectively switching from sensor to sensor. Those sensors which are not 
illuminated due to the darkness of the unobscured portion or width 22 of 
the single band projected on them may be detected and the number of steps 
necessary to provide the switching required recorded as a measure of the 
distance between the first darkened sensor and the second illuminated 
sensor in the array. 
In a typical camera, 512 photodiode elements are arrayed with a spacing 
such that about 0.001 inch exists between each element. These elements are 
about 0.001 inch wide and about 0.10 inch long. A photographic lens 
focuses the image of the unobscured portion of the single band on the 
linear array. The normal lighter color of the wrapper paper results in the 
bulk of the elements receiving sufficient light so that they are fully 
activated. Where the unobscured portion of the single band is present, the 
elements do not receive much light and these elements are not fully 
activated. The elements compose links in a series electrical circuit where 
the degree of activation of the element results in a greater or lesser 
flow of electrical current through the series circuit. A single resistor 
is incorporated into the series circuit and each of the photoelectric 
elements is sequentially switched into the circuit due to the form of the 
array. As each element is switched into the circuit, the resistor develops 
a voltage commensurate with the amount of current permitted to flow 
through it by the photoelement. A large voltage is present for the fully 
lighted photoelements. A markedly lower voltage is present when those 
elements shadowed by the unobscured portion of the single band are in the 
circuit. 
The photoelements are switched into the circuit and out of the circuit by a 
repeating pulse. By counting the number of pulses which occur between the 
voltage decline which takes place on sensing the beginning of the 
unobscured portion of the single band and that which takes place on 
sensing the second end of the unobscured portion of the of the single 
band, it is possible to obtain a precise measurement of the width of the 
unobscured portion of the single band. The precise placement of the 
photoelements in the array makes this possible. Essentially, the 
photoarray measures by counting elements not activated or activated by the 
dark or light image which is to be measured. 
As an example of the invention, a cigarette filter plug machine is fitted 
with an imprinting device consisting of a lithographic offset roll and 
blanket, a permanent plate bearing an image of a single band. A black ink 
is used to imprint the paper. The tack of the ink is reduced to the point 
that the porous paper on which it is imprinted exhibits no tendency to 
pick. 
Once through the imprinting stage, the paper is carried to the point where 
it encircles the fibrous filter core 12 and the seam is formed with a 
2-millimeter overlap of the paper in the seam. After formation of the 
continuous filter rod 25, the rod is passed under the lens system of a 
Reticon linear array camera connected to a Reticon signal processing 
control unit. The controls of the Reticon control unit are adjusted to 
respond to a first black and second light condition and to count the 
number of photoelements arrayed between the first black and second light 
condition. There are 512 lines or photoelements in the Reticon linear 
array. The camera is spaced from the filter rod sufficiently to permit a 
calibration of the number of elements existing between the projected 
images of the unobscured portion of the single band imprinted on the 
filter rod. This calibration permits 450 lines to exist between the first 
black and second light images. The setpoint of the control unit is 
adjusted so that departure of 20 lines plus or minus from this adjustment 
results in triggering of the warning signal attached to the control system 
indicating that the first black and second light edges are too close 
together or too far apart. The number of photoelements chosen corresponds 
to a normal correct displacement of 5 millimeters between the edges of the 
unobscured portion of the single band imprinted on the filter rod. 
When the filter plug machine is operated and the circumference of the 
filter rod being made is less than the desired 27 millimeters, the 
distance between the unobscured portion of the single band edges is 
smaller by the number of millimeters deficient in the circumference. 
Similarly an increase in circumference is accompanied by an increase in 
spacing measured between the unobscured portion of the single band edges. 
Using the electronic readout system permitted adjustment of the unobscured 
portion of the single band until it matches the width of assigned number 
of photoelements. Automatic feedback of the electronic signal to control 
this setting may be accomplished by those skilled in the art. 
In another instance, a cigarette filter plug manufacturing machine is 
equipped with the printer and linear array described above. The experiment 
is run exactly as before with the exception that the digital count 
produced is introduced into a digital comparitor system composed of eight 
Type 7485 digital comparitor chips. The outputs of these chips are 
arranged to provide a positive output consisting of a logical one signal 
when the counter contents exceed the preset indication compared to the 
counter contents. This preset indication is provided by an array of eight 
digital switches producing a binary coded decimal output representative of 
each of the decimal inputs dialed into the switches. The digital 
comparitor also provides a separate logic one output for a determination 
that the counter contents are less than those of the switch array. Each of 
the logic one signals is fed through a separate terminal and consist of a 
voltage which falls to about 1.4 volts for a signal indicating no output 
and 5 volts for a signal indicating output. These signals are supplied to 
solid-stage zero crossover relays which are activated by light-emitting 
diodes optically connected to amplified phototransistors. The logic one 
signals are used to operate the light-emitting diodes of the relays. Thus, 
the presence of a logic one signal results in activating a light-emitting 
diode with the ultimate result that the solid-state relay is closed, 
permitting current to flow to an impulse motor producing one increment of 
movement for each impulse received. The impulse motor is arranged to 
increase the diameter of the filter rod when the logic one signal 
indicates that the rod diameter is less than the set point diameter. It 
also reduces the diameter if the logic one signal indicates that the rod 
is larger than the setpoint. Because of the frequent updating of 
information by the linear array video system measuring the width of the 
unobscured portion of the single band imprinted on the wrapper paper, an 
essentially continuous control of the rod diameter is achieved. 
Porosity of the paper can, in some instances, result in diffusion of the 
inked single band on the paper. This degradation of the edges of the 
single band can be greatly reduced by resort to low-tack lithographic inks 
and the lithographic printing process rather than a fluid ink printed from 
metal dies such as would be done using the letterpress or gravure process. 
In these latter processes, the ink is quite fluid in character and more 
prone to spread in a porous uncoated paper such as is desirable for more 
advanced filter rod construction. 
It will be obvious to those skilled in the art that a single band other 
than that printed in ink may be used in the practice of this invention. 
For example, a magnetic single band, metal reflective, fluorescent, and 
electrically conductive single band may be applied to the paper. 
It is possible to preprint the wrapper paper. The likelihood of large error 
due to stretching or humidity effects on the paper is greatly reduced by 
resorting to printing immediately before the paper enters the plug-making 
machine. 
The measurement system will function well using a linear array video 
camera, an area array video camera, and an electron beam scanned Vidicon 
television tube camera. Video cameras of other design are also operable 
provided the scanning of the image area is precise. Flying spot image 
transducers can be used to pick up the image of the unobscured portion of 
the single band printed on the paper. 
In addition to the television techniques mentioned, tracking photoelectric 
cell arrangements to measure the width of the single band may also be 
utilized. 
Optical means, such as projection microscopes, measuring microscopes, and 
traveling microscopes, can be used to determine the width of the 
unobscured portion of the single band. The methods mentioned utilizing the 
optical techniques are useful for measurement of the band width. They 
offer less utility as a means of pickup of a signal suitable to provide 
automatic control of the filter rod diameter. 
In summary and with reference to FIGS. 6 and 7, therefore, the wrapping 
paper 10 is imprinted with a single band that has a contrasting color with 
respect to the wrapping paper. When the paper is rolled into a cylinder in 
which the axis of the cylinder is parallel to the longitudinal dimension 
of the single band, the resulting structure thus has an overwrap which 
covers or obscures a portion of the single band 18. Since the 
circumference of the cylinder is such that insufficient overwrap is 
available to completely cover the imprinted single band 18, a part of the 
imprinted portion remains exposed or unobscured. Measurement of this 
exposed or unobscured portion by a linear array video camera 24 (FIG. 7) 
or comparable camera will produce a measurement which is related to the 
circumference of the cylinder. 
In an alternate embodiment of the invention, a narrow band 50 is precisely 
positioned with respect to the edges of the wrapping paper 10', leaving a 
wide unprinted area 52 and a smaller unprinted area 54 between the 
imprinted band and the edge of the wrapping paper. When rolled into a 
cylinder, the imprinted narrow band 50 is in ideal circumstances partially 
obscured by the overwrapped paper which completely covers the imprinted 
area 54 and paper edge and partially covers the imprinted narrow band 50. 
The unobscured portion of the narrow band 50 is measured by a linear array 
video camera 24' or comparable camera. The indication of width given by 
the camera is interpreted as tube or cylinder circumference. 
The following examples serve to further illustrate the invention but it 
will be understood that they are included merely for purposes of 
illustration and are not intended to limit the scope of the invention. 
EXAMPLE 1 
In a filter plug manufacturing machine wrapping paper formed of a porous 
paper specially manufactured to permit air flow through the paper around a 
core of crimped continuous cellulose acetate fibers, a single line scan 
television camera manufactured by the Reticon Company of California, 
U.S.A., was arranged to scan a single color strip or band of black ink 
imprinted on the paper wrap by the gravure process. The black strip or 
band was imprinted to bleed over the edge of the wrapper on one edge and 
to form a sharply defined edge of black against the white of the paper on 
the other edge of the band. As the wrapper passed through the machine it 
was rolled to form a cylinder enclosing the fiber core material. At the 
point on the cylinder where the wrapper overwrapped to form a seam, the 
black strip or band was masked by the white edge of the paper so that the 
remaining strip or unobscured portion of the strip or band provided a 
black strip whose width was determined by the amount of overwrap of the 
paper. This arrangement provided a means whereby the camera scanning the 
black strip or unobscured portion of the band could obtain a measurement 
related to the circumference of the filter rod. The amount of black strip 
left showing or unobscured is a measure which can be interpreted in terms 
of the circumference of the filter rod. 
EXAMPLE 2 
As in Example 1, with the exception that the strip or band of black was 
imprinted by the offset lithographic process. 
EXAMPLE 3 
As in Example 1, with the exception that the strip or band of black was 
imprinted by the letterpress printing process. 
EXAMPLE 4 
As in Example 1, with the exception that the strip or band of imprinting 
was done in red ink, and the Reticon camera was fitted with a green filter 
to provide a suitable color contrast. 
EXAMPLE 5 
As in Example 1, with the exception that the unobscured portion of the 
strip or band was scanned by a projection optical system which projected 
the image of the strip or band on an engraved screen for comparison with 
the engraved reticle on the screen. 
EXAMPLE 6 
As in Example 1, with the exception that the imprinted band was narrow (one 
millimeter in width), did not bleed over the edge of the strip of paper, 
and was precisely positioned with respect to the edges of the wrapping 
paper. This offered reference points from which the circumference of the 
cylinder could be determined. 
The process described is subject to error due to paper stretch. Errors due 
to location of multiple lines or errors due to error in line width 
printing, as disclosed in our copending application, are reduced since 
only a single band of color is imprinted. The system does require some 
calibration since the positioning of the imprinted edge of the color band 
must be precise with respect to one or both edges of the paper wrap. 
Further, the width of the paper wrap must be precisely controlled in the 
slitting process. 
An imprinted band having a breadth sufficient to extend to the sharply 
defined edge between the imprinted and unimprinted area offers the 
greatest flexibility in application of the measuring and manufacturing 
process. Such a band permits wide variation in the circumference of the 
tube while assuring that no ambiguities will ensue due to the formation of 
tube circumferences which will result in total obscuration of the 
imprinted band, since it is only necessary to assure that the band is 
imprinted with sufficient breadth to serve in all circumstances. In a 
second instance it has been found that a narrow band correctly positioned 
to serve for a carefully determined range of circumferences offer 
aesthetic advantages and a further advantage of visual detection of 
excessively small circumference. When such a band is imprinted it is 
essential that it be so positioned that for all circumferences envisioned, 
the overwrap portion will never totally obscure the imprinted band. If 
total obscuration occurs, it is an indication that the circumference of 
the tube is too small. 
Some additional advantage is inherent in the narrow band in that it is 
possible to arrange it so that only a very thin width of band is exposed 
by the shortfall of the overwrap. When this is the case, it is possible to 
arrange the line scan television camera to view this narrow band and 
interpret it in terms of the high ratios which take place when variation 
in the band width is present. When the ratio of change to total exposed 
width is calculated, very narrow widths result in the changes in width 
appearing large when calculated in terms of the change versus the total 
exposed width. Such an arrangement has been found to offer great 
sensitivity in determining the change in circumference. 
With respect to aesthetic advantages of the narrow imprinted band, the 
narrowness of the line renders it less obtrusive and thus less 
objectionable to those who view any imprinting of the tubular 
configuration as a marring element. 
The invention has been described in detail with particular reference to 
preferred embodiments thereof, but it will be understood that variations 
and modifications can be effected within the spirit and scope of the 
invention.