On-line color monitoring and control system and method

An on-line color monitoring and control system and method includes feeding of colorant in a given amount or ratio in order to achieve a desired color of a product. The system and method described here achieve reliable on-line color control of synthetic fibers, single moving yarn (or fiber) or a collection of moving fibers. The color characteristic of the product is sensed and processed to generate a control signal for adjusting the amount of colorant being fed. Color measurement takes place either prior to or after spooling of the product.

TECHNICAL FIELD 
The present invention generally relates to on-line color monitoring and 
control of fibers produced by an extrusion device. More specifically, the 
invention relates to the measurement of the color of moving yarn or fibers 
soon after extrusion. Two alternative sensor mechanisms are disclosed--one 
which measures color prior to spooling of the product, and another which 
measures color after the product is collected on the spool. In addition, 
the color measurement signal is quickly checked against a reference signal 
using an optical switch. 
BACKGROUND ART 
In the past, the color of a product produced by an extrusion device has 
been monitored and controlled in an off-line manner. Typically, the 
extrusion device or system would be operated until color equilibrium was 
achieved, followed by collection of a product having a certain color. The 
spool of collected product would then be removed from the system, and 
taken to a color laboratory where the color would be measured using an 
off-line spectrometer. Then, once a color evaluation was made, the spool 
would be returned to the extrusion device or system, adjustments would be 
made to the level of the colorant provided to the extrusion device, and 
another run of about ten minutes or so would be commenced. This process 
would be repeated until evaluation of the color of the product in the 
color laboratory indicated that the desired color, within acceptable 
limits, had been achieved. 
The latter process was not only time-consuming and inefficient, but also 
resulted in substantial waste. That is to say, a large amount of scrap 
material was produced and wasted during each run. Thus, if several runs 
during a given period of time were necessary in order to evaluate and 
adjust the color of the product, a very substantial amount of waste 
material would result. 
The latter system or process was also inefficient from the standpoint of 
time in that each run would take about ten minutes or so, and then the 
color evaluation in the laboratory would take another thirty minutes to 
one hour. Thus, if several repetitions of the evaluation process were 
necessary before the final acceptable coloration was achieved, the entire 
pre-production process could take several hours. 
Accordingly, there has been a need for the development of an on-line color 
monitoring and control system and method. Moreover, there is a need for 
the development of such an on-line color monitoring and control system and 
method employing the most modern optical technology for both transmission 
of incident light toward the product and reflection of light from the 
product, as well as handling and transfer of the light through an optical 
spectrum analyzer to that portion of the system which actually performs 
the evaluation of the coloration of the product. 
It is recognized that on-line measurement of the color of extruded pellets 
in compounding operations is known in the art. For example, see the 
following: U.S. Pat. No. 3,972,854--Costolow and U.S. Pat. No. 
5,559,173--Campo. In addition, on-line color control of fiber extrusion 
has been achieved by measuring the color of a fiber melt. In this regard, 
see U.S. Pat. No. 4,684,488--Rudolph. 
Nevertheless, measurement of the color of moving yarn or fiber (or a 
filament of a yarn), or of a collection of fibers, is not known in the 
prior art. Moreover, the employment of alternative sensor mechanisms for 
measuring color of an extruded product prior to spooling and on-spool, 
respectively, is also not known in the art. Finally, employment of means 
for quickly checking the color measurement signal against a reference 
signal, and specifically use of an optical switch to accomplish that 
purpose, are also not known in the art. 
Therefore, there is a need in the art for development of an on-line color 
monitoring and control system and method which measures the color of 
moving yarn or fiber (or filament of a yarn), or of a collection of 
fibers. Mechanisms for measurement of color both prior to spooling and 
on-spool are also needed. Finally, a means for quickly checking the color 
measurement signal against a reference signal, using an optical switch, is 
also needed. 
The following patents are considered to be of background interest relative 
to the present invention, and are burdened by the disadvantages of prior 
art methods and arrangements, as discussed above: U.S. Pat. No. 
5,526,285--Campo et al.; U.S. Pat. No. 5,468,586--Proper et al.; U.S. Pat. 
No. 5,387,381--Saloom; U.S. Pat. No. 5,282,141--Faas et al.; U.S. Pat. No. 
5,092,168--Baker; U.S. Pat. No. 5,053,176--Cameron et al.; U.S. Pat. No. 
4,788,650--Willis et al.; U.S. Pat. No. 4,761,129--Aste et al.; U.S. Pat. 
No. 4,745,555--Connelly et al.; U.S. Pat. No. 4,688,178--Connelly et al.; 
U.S. Pat. No. 3,388,261--Roberts et al.; 
DISCLOSURE OF INVENTION 
The present invention generally relates to an on-line color monitoring and 
control system and method, and more particularly to a system and method 
for measuring the color of a product produced by an extrusion device, 
determining whether the color falls within acceptable limits, and 
increasing or decreasing the level of the colorant provided to the 
extrusion device so as to adjust the color of the product. 
As discussed in more detail below, the system of the present invention is 
utilized with an extrusion system. More importantly, the system of the 
present invention employs a color sensing arrangement which, in 
conjunction with an optical spectrum analyzer (OSA), provides a color 
sensor signal to a module (typically, a digital computer). The latter 
provides a serial data output to a programmable logic controller (PLC), 
which provides control signals to the feeder/mixer arrangement of the 
extrusion system for the purpose of adjusting the colorant level of the 
raw material provided to the extrusion device. Finally, in accordance with 
the invention, the PLC also provides an output to a network for the 
purpose of providing status information and the like. 
It is to be further understood that, in accordance with the invention, a 
specially designed optical switch is provided for selecting between a 
reference signal and a measurement signal so as to provide a corresponding 
output to the OSA or spectrometer. In addition, in one embodiment, the 
inventive system employs a spring-loaded, twin-roller measuring 
arrangement for a light receiver so as to perform color measurement "on 
spool," and to provide a light measurement signal to the OSA. In a further 
embodiment of the invention, a yarn guide is employed and color 
measurement is performed prior to spooling of the material in question. 
Finally, in accordance with the invention, the color monitoring and 
control system is software-controlled via a programmed element or PLC 
connected, via a serial data communications link, to a personal computer. 
Therefore, it is a primary object of the present invention to provide an 
on-line color monitoring and control system and method. 
It is an additional object of the present invention to provide a system and 
method for measuring the color of a product produced by an extrusion 
device. 
It is an additional object of the present invention to provide a system and 
method which determine whether the color of an extruded product falls 
within acceptable limits. 
It is an additional object of the present invention to provide a system and 
method which increases and decreases the level of colorant provided to an 
extrusion device so as to adjust the color of the extruded product. 
It is an additional object of the present invention to provide a color 
monitoring and control system which employs a specially designed optical 
switch for selecting between a reference signal and a measurement signal. 
It is an additional object of the present invention to provide a color 
monitoring and control system which, in one embodiment employs a 
spring-loaded, twin-roller measuring arrangement to provide "on spool" 
color measurement of a product. 
It is an additional object of the present invention to provide a color 
monitoring and control system which, in another embodiment, employs a yarn 
guide to perform color measurement prior to spooling of the product in 
question. 
It is an additional object of the present invention to provide a color 
monitoring and control system which is software-controlled via use of a 
programmed element, such as a PLC, connected via a data communications 
link to a personal computer. 
The above and other objects, and the nature of the invention, will be more 
clearly understood by reference to the following detailed description, the 
associated drawings, and the appended claims.

BEST MODE FOR CARRYING OUT THE INVENTION 
The invention will now be described in more detail with reference to the 
various figures of the drawings. 
FIG. 1 is a general block diagram of the color monitoring and control 
system of the present invention. As seen therein, the on-line color 
monitoring and control system 10 comprises feeders 12 and 14 connected via 
control valves 16 and 18, respectively, to a mixer 20. The mixer 20 has 
its output side connected to an extruder 22, and the extruded output 
material thereof proceeds past a line break sensor 24 to a spool 26, on 
which the extruded material is wound. 
The system 10 further includes a color sensor 28 disposed adjacent to the 
spool 26, the output of the color sensor 28 being connected via an optical 
spectrum analyzer (OSA) or spectrometer 30 to a module 34, which is 
implemented by a computer. The output of module 34 is connected to the 
input of programmable logic controller (PLC) 36, and the output of PLC 36 
is provided to a network 38. In addition, the PLC 36 provides control 
outputs to the control valves 16 and 18, respectively. 
In operation, feeder 12 is typically loaded with raw material, such as 
nylon material, to be mixed and extruded, while feeder 14 is typically 
loaded with colorant in order to provide coloration of the material from 
feeder 12 once the two constituents are mixed in mixer 20. In response to 
control signals from PLC 36, valves 16 and 18 provide a corresponding flow 
of nylon raw material and colorant from feeders 12 and 14, respectively, 
to the mixer 20, in which those materials are mixed. The resultant mixed 
material is then provided to an extruder 22 which, in accordance with a 
conventional extruding process, produces extruded material which is 
conveyed past the line break sensor 24 to the spool 26, on which the 
extruded material is wound. 
Color sensor 28, which is disposed adjacent to the spool 26, operates in a 
manner to be described in more detail below to generate an optical signal 
output corresponding to the color of the material wound on spool 26 as 
sensed by the sensor 28. The optical signal output of sensor 28 is 
provided to OSA 30, wherein it is converted into an analog electrical 
signal output for provision to the module 34. 
As previously mentioned, module 34 is, preferably, a computer which 
receives the analog signal input from OSA 30, converts it into digital 
form, and then provides a corresponding serial data output to the PLC 36. 
PLC 36 operates, in a manner to be described in more detail below, to 
determine the coloration of the material wound on spool 26, compare it to 
a desired coloration within acceptable standards, and generate control 
signals for adjusting the flow rate of the nylon material in feeder 12 
and/or the colorant contained in feeder 14 (via valves 16 and 18, 
respectively) in order to vary the input to mixer 20, and thus vary the 
coloration characteristics of the mixed material provided by mixer 20 to 
extruder 22. In addition, PLC 36 provides an information output to a 
network 38 for dissemination to various personnel involved in or 
responsible for the operation of the on-line color monitoring and control 
system 10. 
Keyboard 32 is provided in order to receive operator inputs to the system 
10, and provides such operator inputs to the module 34. Such operator 
inputs are provided in order to initiate the operation of the system 10, 
to set parameters (such as initial feed settings for feeders 12 and 14), 
and to control the operation of the system during the on-line color 
monitoring process. 
Line break sensor 24 is a conventional device for sensing a break in the 
line of extruded material provided by extruder 22 to the spool 26. If 
there is such a break, sensor 24 operates in a conventional manner to 
provide an alert signal to the module 34. 
FIG. 2 is a diagrammatic representation of the on-line color sensor 
employed in the system of FIG. 1. As seen therein, on-line color sensor 28 
comprises a measurement spool arrangement 50 and a white reference 
arrangement 52 in combination with optical fiber connections 54, 56, 58 
and 60 and optical switch 62. As seen in FIG. 2, a light source 64 
provides an optical input to both measurement spool arrangement 50 and 
white reference arrangement 52. More specifically, the light output of 
source 64 is provided via optical fiber connections 58 and 60 to 
measurement spool arrangement 50. 
The measurement spool arrangement 50 transmits the light toward the 
material being wound on spool 26 (FIG. 1), and receives reflected light 
therefrom. The reflected light is provided via optical fiber connections 
54 and 56 to one input of the switch 62, the other input of which receives 
white reference light reflected from white reference arrangement 52 as a 
result of the reception, by arrangement 52, of incident light from the 
light source 64. 
Optical switch 62 operates, in a manner to be described in more detail 
below, to select either the reference light from arrangement 52 or the 
reflected measurement light from measurement arrangement 50 for input to 
the OSA 30. 
FIG. 3 is a diagram of an optical switch employed in the on-line color 
sensor of FIG. 2. As seen therein, optical switch 62 comprises the 
following elements: lever 81, motor shaft 82, optical fiber connector 83, 
grooved track 84, frame 85, contact element 86, microswitches 87a and 87b, 
optical fiber inputs 88 and 89, optical fiber output 90, and motor 91. 
In operation, motor 91 drives lever 81 alternately between positions 84a 
and 84b in the grooved track 84. That is to say, lever 81 is first driven 
in the direction of arrow A so as to come to rest in position 84a, and is 
then driven in the direction of arrow B so as to come to rest in position 
84b. In position 84a, the optical fiber input 88 from measurement 
arrangement 50 (FIG. 2) is connected to the optical fiber output 90. 
Alternatively, in position 84b, the optical fiber input 89 from reference 
arrangement 52 (FIG. 2) is connected to the optical fiber output 90. 
Optical fiber output 90 provides its optical fiber output to the OSA 30, 
as previously described above with respect to FIGS. 1 and 2. 
Further referring to FIG. 3, when the optical fiber connector 83 of lever 
81 is in position 84a, contact element 86 contacts microswitch 87a, 
thereby providing an information signal to module 34. Similarly, when 
optical fiber connector 83 of lever 81 is in position 84b, the contact 
element 86 contacts microswitch 87b, thereby providing a further 
information signal to module 33. 
Motor 91 is programmed or controlled to alternately rotate motor shaft 82 
in one of two directions, as indicated by the double-headed arrow C in 
FIG. 3. In this manner, the lever 81 and its associated optical fiber 
connector 83 are moved alternately in the directions indicated by the 
arrows A and B, respectively. That is to say, motor 91 moves lever 81 in 
the direction indicated by arrow A in FIG. 3 until it reaches position 
84a, where it is stopped by the endwall of the slot 84. Similarly, motor 
91 moves lever 81 in the direction indicated by arrow B until it reaches 
position 84b, where it is stopped by the endwall of slot 84. 
With respect to the operation of the motor 91 of FIG. 3, preferably, motor 
91 is normally driven in the clockwise direction by a drive signal from 
module 34 of FIG. 1. The motor 91 drives the lever 81 through a rubber 
linkage 82a (seen in FIG. 3) so that, once the lever 81 has been stopped 
by the endwall of slot 84 at position 84a, motor 91 continues to drive and 
puts the rubber linkage 82a in torsional tension, thereby firmly pressing 
the lever 81 against the right hand endwall of slot 84 at position 84a. 
When rod 86 arrives at its leftmost position and contacts microswitch 87a, 
an information signal is sent to module 34 (FIG. 1), and the module 34 
cuts off the motor 91. 
Preferably, motor 91 is a stepper motor, which has a holding torque when 
not moving so that the rubber linkage 82a is held in light torsion and the 
lever 83 is pressed against the end of the slot 84. In position 84a, a 
color measurement signal received via input optical fiber 88 is provided 
via output optical fiber 90 to module 34. Holding the lever 83 with 
positive pressure against the end of the slot 84 gives good optical 
alignment repeatability, and this has been estimated to be better than 
fifty micrometers. 
With respect to the second cycle of operation of the lever 81 and motor 91, 
the module 34 is programmed so that, after a predetermined period of time 
(for example, once every hour or so), the motor 91 is driven by module 34 
in the counter-clockwise direction, thereby changing the position of the 
lever 83. In this manner, the lever 83 is driven in the direction of arrow 
B so as to arrive at position 84b in grooved track 84. At that point, rod 
86 contacts microswitch 87b so that module 34 cuts off motor 91, and 
module 34 takes a measurement of the reference signal provided via input 
optical fiber 89 (FIG. 3) and output optical fiber 90. Once the 
measurement of the reference signal is taken, module 34 places optical 
switch 62 into its original state so that another measurement cycle can 
commence. 
FIG. 4 is a side, cross-sectional view of a bobbin and roller, showing use 
of the twin-roller measuring arrangement of the present invention. As seen 
therein, the twin-roller measurement arrangement 50 comprises rollers 100 
and 101 which are joined by a connecting frame 102 which is urged in a 
direction toward the spool 26 by a spring 103. Light generated by the 
source 64 (FIG. 2) is conveyed to a point located between the rollers 100 
and 101 by optical fiber 50a, and light reflected from the material wound 
on the spool 26 is conveyed away from a position between rollers 100 and 
101 by optical fiber 50b and, as previously mentioned, is provided via 
optical fiber connectors 54 and 56 and optical fiber input 88 to the 
optical switch 62 (FIG. 2). 
In operation, spool 26 is rotated under the influence or urging of a 
rotating support 104. Preferably, rotating support 104 is firmly fixed in 
space and cannot move except for rotation. The spool 26 is free to move 
away from support 104 as it grows. The center of spool 26 actually traces 
an arc in the plane of FIG. 4 (if such an arc were to be plotted). Thus, 
in the preferred embodiment, pivoting action between connecting frame 102 
and spring 103 takes place via the pivotal connection 103a therebetween. 
It should be recognized that, although not shown in FIG. 4, the spool 26 
has a motor attached to its central axle 26a so that the spool 26 is 
rotatable. Moreover, the entire arrangement--spool 26, axle 26a and the 
spool motor (not shown)--is movable as the spool 26 rotates and is filled, 
and thereby moves away from the rotating support 104 in the direction 
generally indicated by the arrow D in FIG. 4. 
The twin-roller arrangement 50 is maintained in its position with respect 
to the rotating spool 26 as a result of the combined influence of the 
spring 103 (which urges the rollers 100 and 101 toward the spool 26) and 
the rotational capability of the rollers 100 and 101. As the spool 26 and 
the material wound thereon pass by the rollers 100 and 101, light provided 
by source 64 (FIG. 2) is conveyed via optical fiber 50a so that the light 
is incident on the surface of the material wound on spool 26. As a result, 
light is reflected from the material on spool 26, and such reflected light 
is conveyed away from spool 26 and rollers 100, 101 by optical fiber 50b. 
Such reflected light, as previously mentioned, is conveyed via optical 
fiber connectors 54 and 56 and optical fiber input 88 to the optical 
switch 62. 
FIG. 5A is a perspective view of a yarn guide employed in the color sensor 
of the present invention. The arrangement shown in FIG. 5A constitutes an 
alternative embodiment for light measurement, that is, an alternative to 
the twin-roller measuring arrangement 50 generally shown in FIG. 2 and 
described in more detail relative to FIG. 4. 
As seen in FIG. 5A, yarn guide 120 comprises a U-shaped light shield 122 
which, on one side thereof, receives a fiber optical bundle 124. A 
stainless steel block 126 having a slot 128 formed therein is mounted on 
an interior surface of the U-shaped light shield 122. 
In operation, material emerging from the extruder 22 (FIG. 1)--for example, 
yarn 130 shown in FIG. 5A--is conveyed through the slot 128, in which the 
yarn 130 passes adjacent to illuminating fibers 124a contained within the 
bundle 124. Illuminating fibers 124a convey light toward the yarn 130 so 
as to illuminate the yarn 130, and light reflected therefrom is conveyed 
back through receiving fibers 124b in the bundle 124. Once the yarn 130 
passes adjacent to fiber optic bundle 124, it is conveyed out the lower 
end of yarn guide 120 toward the spool 26. 
FIG. 5B is a further view of the yarn guide of the present invention 
employed with a fiber bundle for the purpose of transmission of light to 
the yarn guide and reception of sensed light from the yarn guide. In 
accordance with this embodiment of the invention, the yarn or fiber 130 is 
subjected to color measurement just as the individual extruded filaments 
132 emerging from the extruder 22 (FIG. 1) are collected together. 
Filaments 132, once collected, form a neat reproducible ribbon of yarn 
130, and are measured just before they pass through a conventional 
lubrication applicator (not shown). 
The ribboned yarn 130 is measured, as previously described, by shining 
white light from source 64 (FIG. 2) on the yarn 130, and measuring the 
reflected or scattered light by conveying such reflected or scattered 
light through optical switch 62 to the OSA 30 (FIG. 2). In practice, a 
fiberoptic bundle 124 is utilized and, as previously described, the bundle 
124 has half of its elements in the form of illuminating fibers 124a and 
the other half of its elements in the form of receiving fibers 124b (see 
FIGS. 5A and 5B). 
FIGS. 6A and 6B are flowcharts of software operations performed by the 
module (personal computer) and PLC in accordance with the present 
invention. 
More particularly, FIG. 6A is a flowchart of the operations performed by 
the module 34 of FIG. 1. In that regard, module 34 of FIG. 1 is, 
preferably, a programmed personal computer which receives analog color 
sensor signals from the OSA 30. Accordingly, module 34 is equipped with an 
analog-to-digital converter (ADC) card or other means for digital 
conversion, thereby converting the analog color sensor signals from the 
OSA 30 to digital form prior to provision to the processor of the personal 
computer or module 34. Such digital data are then processed by the 
processor of the personal computer or module 34 in accordance with the 
flowchart of FIG. 6A. 
Considering the flowchart of FIG. 6A in detail, the processing operation is 
commenced (block 200), and a target color is selected from a list of 
target colors (block 201). This selection of a target color is typically 
performed in response to an operator input via keyboard 32 of FIG. 1. 
Continuing with the flowchart of FIG. 6A, in the manner described above, 
the color of the product wound on spool 26 is measured (block 202), and an 
error or disparity between the measured color and the target color is 
calculated (block 203). A determination is then made as to whether or not 
the measured color falls inside a tolerance band or acceptable limit of 
deviation between measured color and target color (block 204). If the 
color is not inside the tolerance band, then an alarm (e.g., a red 
indicator) is displayed on the console (block 205). 
If the color is inside the tolerance band, a determination is made as to 
whether the color is inside the middle two quartiles of the tolerance band 
(block 206). If the color is not inside the middle two quartiles of the 
tolerance band, an alarm (e.g., an amber indicator) is displayed (block 
207). In the latter regard, it has been found to be convenient to use the 
red/amber alarm indicator system analogous to the stop/caution indicators 
in traffic light systems. If the color is inside the middle two quartiles 
of the tolerance band, the target color has been achieved within 
acceptable limits, and the color sensing and control process is terminated 
(block 210). 
Once a red alarm (block 205) or an amber alarm (block 207) is displayed, a 
further determination is made as to whether a time period of greater than 
the dwell time since the last adjustment in colorant color has passed. In 
the latter regard, "dwell time" is defined as the length of time that it 
takes for colorants to travel through the extruder. If more than the dwell 
time has passed since the last adjustment of coloration, the module 34 
instructs the PLC 36 to increase colorant level if color is too light or 
to decrease colorant level if the color is too dark (block 209). This 
process will be described in more detail below with respect to FIG. 6B. On 
the other hand, if more than seven minutes has not passed since the last 
adjustment in coloration, no action is taken, and the process merely 
returns to the color measurement step (block 202). 
The operations performed by the PLC 36 of FIG. 1 will now be described with 
reference to the flowchart of FIG. 6B. The PLC 36 commences operation 
(block 220), and the operator enters feed settings for the valves 16 and 
18 associated with feeders 12 and 14, respectively, of FIG. 1 (block 221 
of FIG. 6B). The PLC 36 then performs no further operation until it 
receives input from the module 34 as a result of color measurement 
performed in accordance with the flowchart of FIG. 6A. If, as a result of 
the flowchart of FIG. 6A, it is determined that color adjustment is 
needed, and if there has been more than seven minutes since the last 
adjustment in color (see blocks 205, 207 and 208 of FIG. 6A), then an 
increase or decrease in colorant level is indicated, and the PLC 36 
responds to a control input from the module 34 by increasing or decreasing 
the colorant color according to the color measurement (see block 222 of 
FIG. 6B). 
As a next step, the PLC 36 determines whether the feed levels for feeders 
12 and 14 of FIG. 1 are within acceptable limits (block 223). If the feed 
levels are within acceptable limits, then the PLC 36 awaits further 
control input from the module 34 and further adjusts colorant color based 
on color evaluation performed by the module 34 (block 222 of FIG. 6B). 
If the feed levels are not within acceptable limits (block 223), original 
feed settings for the valves 16 and 18 are restored by the PLC 36 (block 
224 of FIG. 6B), and an alarm is sounded (block 225). Once the alarm is 
sounded, PLC 36 then awaits further control inputs from the operator via 
keyboard 32 or from the module 34 as a result of further color evaluation. 
While preferred forms and arrangements have been shown in illustrating the 
invention, it is to be understood that various changes and modifications 
may be made without departing from the spirit and scope of this 
disclosure.