U.S. patent number 3,731,069 [Application Number 05/175,485] was granted by the patent office on 1973-05-01 for apparatus for detecting yarn quality information.
Invention is credited to Tsugio Goto, Tsutomu Tamura.
United States Patent |
3,731,069 |
Goto , et al. |
May 1, 1973 |
APPARATUS FOR DETECTING YARN QUALITY INFORMATION
Abstract
Yarn evenness or nonuniformity in thickness or mass of
filamentary or film-shaped yarns formed of synthetic polymers,
natural or regenerated celluloses or the like is detected in the
form of electrical deviation signals, which are applied first to an
areal average detector circuit to provide an areal average,
lengthwise of the yarn, of irregularities, secondly to a peak value
detector circuit to provide an average of crest values lengthwise
of the yarn of the irregularities, and thirdly to an abnormality
detector circuit to detect abnormally thick yarn portions such as
fluff or slub which occur isolatedly or to detect filament
abnormalities in a multi-filament yarn which also occur isolatedly.
These detected outputs are derived from a running yarn or yarns
travelling through a yarn production, finishing or false twist
process and are adapted to be utilized in an electronic computer
for overall evaluation to determine the yarn quality.
Inventors: |
Goto; Tsugio (Nobeoka,
JA), Tamura; Tsutomu (Nobeoka, JA) |
Family
ID: |
27518408 |
Appl.
No.: |
05/175,485 |
Filed: |
August 27, 1971 |
Foreign Application Priority Data
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Aug 29, 1970 [JA] |
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45/75757 |
Nov 4, 1970 [JA] |
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45/97368 |
Nov 4, 1970 [JA] |
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45/97369 |
Feb 3, 1971 [JA] |
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46/3908 |
Feb 1, 1971 [JA] |
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46/3909 |
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Current U.S.
Class: |
700/144; 73/160;
340/677; 702/170; 702/35; 702/173; 28/227 |
Current CPC
Class: |
G01N
33/365 (20130101) |
Current International
Class: |
G01N
33/36 (20060101); G06g 007/66 () |
Field of
Search: |
;235/151.1,151.3
;340/178,259 ;324/61R,71R ;73/159-160 ;28/64,72R ;250/219WE,219TH
;57/81 ;242/36 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Morrison; Malcolm A.
Assistant Examiner: Smith; Jerry
Claims
Having described the invention, what is claimed is:
1. Apparatus for detecting yarn quality information comprising a
device for producing a deviation signal which varies in accordance
with the irregularities in thickness or mass of a length of yarn
being monitored, an areal average detector circuit responsive to an
areal average of the deviation signal to produce an areal average
signal representative of the average value of the irregularities
occurring along the length of yarn, and a peak value average
detector circuit responsive to an average of peak values of the
deviation signal to produce a peak average signal representative of
the average of peak values of the irregularities occurring along
the length of yarn, said areal average and peak average signals
being indicative of the quality of the yarn.
2. Apparatus according to claim 1, further including a circuit for
rectifying the deviation signal, and a yarn cut detector circuit
for detecting the reduction of the rectified output below a given
level.
3. Apparatus according to claim 1, in which the areal average
detector circuit comprises a circuit for detecting one polarity of
the deviation signal, a time constant circuit constituted by a
capacitor and a resistor to which said detected signal of said one
polarity is supplied, the time constant circuit having a charging
time constant which is greater than pulse widths of the deviation
signal and having a discharge time constant which is chosen less
than time intervals between adjacent occurring pulses, and a
circuit for averaging out the signal developed across said resistor
of the time constant circuit.
4. Apparatus according to claim 1, in which the areal average
detector circuit comprises a first detector circuit for detecting
one polarity of the deviation signal, a second detector circuit for
detecting the other polarity of the deviation signal, and a circuit
for adding the outputs from the first and second detector circuits
together with a same polarity and averaging out the result.
5. Apparatus according to claim 1, in which the peak average
detector circuit comprises a voltage doubler rectifier of the type
in which a peak value is detected.
6. Apparatus according to claim 1, in which the deviation signal
producing device comprises transducer means for varying the voltage
of a high frequency electrical signal in a capacitive transducing
fashion in accordance with irregularities in thickness or mass of
the yarn, a rectifier circuit for rectifying the converted high
frequency electrical signal, said rectifier circuit having a noise
response which is reduced at relatively low frequencies, and an
amplifier with negative feedback to which the rectified output is
supplied and having a frequency response to block frequencies less
than that corresponding to the length of the longest extending
irregularity to be monitored.
7. Apparatus for detecting yarn quality information comprising
means provided separately for a plurality of running yarns to be
measured for producing a deviation signal which varies in
accordance with irregularities in thickness or mass of each yarn
being measured, scan means for deriving the deviation signals
successively, an areal average detector circuit which is supplied
with the output of the scan means, a peak value average circuit for
producing an average of peak values of yarn evenness, and means for
collectively evaluating the outputs of the areal average detector
circuit and the peak value average circuit for each yarn to derive
information concerning the quality and grade of each yarn being
measured.
8. Apparatus according to claim 7, further comprising a circuit
supplied with the output of the scan means for detecting isolatedly
occurring abnormal levels of the deviation signal, the output from
the last mentioned circuit being also fed to the evaluating
means.
9. Apparatus according to claim 7, further comprising a filter
circuit supplied with the output of the scan means for detecting
low frequency components thereof, and an abnormally low level
detector circuit for detecting the low frequency components below a
given level, the output of the last mentioned detector circuit
being also fed to the evaluating means.
10. Apparatus according to claim 7, further comprising means for
issuing a yarn cutting instruction for a yarn being measured which
is determined to be of defective quality by the evaluating means, a
circuit for producing a yarn cutting signal in response to the yarn
cutting instruction, and means associated with each of the yarns
being measured to cut a running yarn at a given location thereof in
response to the yarn cutting signal.
11. Apparatus according to claim 10, in which the yarn cutting
means is interposed between the deviation signal detecting means
and the scan means, the arrangement being such that a signal of
high level is produced upon disappearance of the deviation signal
from the deviation signal detecting means, said signal of high
level being effective to operate the yarn cutting means.
12. Apparatus according to claim 7, further comprising means for
deriving from the output of the areal average detector circuit
information concerning shading formed upon dyeing a cloth woven
from the yarn being measured and for deriving from the output of
the peak value average detector circuit information concerning dye
streaking.
13. Apparatus according to claim 7, in which the evaluating means
stores the outputs of the areal average detector circuit and the
peak value average detector circuit separately for each of the
yarns being measured and determines the quality grade of the yarns
being measured on the basis of the stored outputs.
14. Apparatus according to claim 13, further comprising means for
according to the outputs from the detector circuits differential
weights according to the variety of the detector circuit before
being added together, the sum being made the basis to determine the
quality grade of a corresponding yarn being measured.
15. A method of measuring the quality of yarn comprising the steps
of:
producing a deviation signal which varies in accordance with the
irregularities in thickness or mass which occur along a length of
the yarn;
averaging said deviation signal to produce an areal average signal
representative of the average value of irregularities occurring
along the length of yarn;
averaging the peak values of said deviation signal to produce a
peak average signal representative of the average of the peak
values of irregularities occurring along the length of yarn;
and
using said areal average signal and said peak average signal as a
measure of the quality of the length of yarn.
16. A method according to claim 15 further comprising the step of
determining from said areal average and peak average signals the
dyeing grade of the length of yarn.
17. A method according to claim 16 further comprising the step of
determining from said areal average signal information concerning
dye shading which would occur in the yarn when it is subsequently
formed into cloth and dyed.
18. A method according to claim 17 further comprising the step of
determining from said peak average signal information concerning
dye streaking which would occur in the yarn when it is subsequently
dyed.
Description
The invention relates to an apparatus for electrically detecting
nonuniformity or irregularities in thickness or mass of filamentary
or film-shaped yarns formed of synthetic polymers, natural or
regenerated celluloses or the like and for deriving from these
electrical deviation signals information determining the quality of
yarns.
The prior art practice in determining the quality of yarns involved
extracting pirns on which yarns obtained from a number of spindles
are wound, and weaving or knitting a cloth with a portion of yarns
on the pirns for the purpose of quality control, the cloth being
dyed to observe whether or not the dyeing can take place uniformly
or includes shading and dyeing streak for final evaluation of the
yarns from selected pirns or spindles. The appearance of the pirn
was also examined to determine the yarn quality as to large
irregularities such as fluffs. Such a prior art procedure for
determination of yarn quality is basically a sampling inspection
system which cannot provide for an accurate estimate of the overall
product, and in addition requires much labor and time inasmuch as
the inspection calls for a cloth to be woven or knitted, dyed and
visually examined. Moreover, the visual inspection relies on the
skill and/or experience of the inspectors, which renders it
unavoidable that the evaluation varies from inspector to inspector,
thereby resulting in a failure to provide an objective
evaluation.
It is known that the most significant factor which determines the
yarn quality when a filamentary or film-shaped yarn is produced or
processed is nonuniformity information concerning the thickness or
mass of the yarn. However, there has been no attempt to derive yarn
quality information directly from such nonuniformity information
while the latter is being detected in the process of yarn
production or processing, without recourse to the above mentioned
labor and time consuming inspection procedure. It is apparent that
it is convenient to have such nonuniformity information detected in
the process of yarn production or processing directly and
continuously converted to a yarn quality information in order to
enable an on-line production and processing control by allowing
immediate actions to be taken in response to such quality
information.
Therefore, it is an object of the invention to provide an apparatus
for detecting yarn quality information in an accurate and rapid
manner.
It is another object of the invention to provide an apparatus for
detecting yarn quality information which permits continuous and
immediate estimation of yarn quality in an on-line manner, i.e.,
during yarn production or processing steps.
It is a further object of the invention to provide an apparatus for
detecting yarn quality information which is capable of providing an
average value of yarn irregularities as well as an indication of
detection of isolatedly occurring increased or decreased yarn
thickness or cut in the yarn.
It is still another object of the invention to provide an apparatus
for detecting yarn quality information having an areal irregularity
average detector circuit which provides, even in the presence of a
great variation of the magnitude of yarn irregularities and of
their occurrence, an electrical signal which properly corresponds
to an average of areas of irregularities over the yarn length.
It is a still further object of the invention to provide an
apparatus for detecting yarn quality information which includes a
peak irregularity average detector circuit capable of faithfully
sensing the average of peak values of yarn irregularities over the
yarn length.
It is yet another object of the invention to provide an apparatus
for detecting yarn quality information which provides for
simultaneous detection of quality information of yarns supplied
from a plurality of spindles, by using a single common unit.
It is a further object of the invention to provide an apparatus for
detecting yarn quality information which detects yarn
irregularities of various kinds and collectively puts these
information into account to determine the yarn quality.
It is a still further object of the invention to provide an
apparatus for detecting yarn quality information which includes
means to cut a defective yarn upon over-all determination of yarn
quality.
It is another object of the invention to provide an apparatus for
detecting yarn quality information which includes yarn cutting
means capable of cutting a yarn from a particular spindle without
adverse effect upon other spindles, that is, without cutting yarns
from these other spindles.
It is still another object of the invention to provide an apparatus
for detecting yarn quality information which includes yarn cutting
means adapted to be controlled by a yarn cutting instruction
derived from yarn nonuniformity information and controlled also
directly by an electrical output representing yarn irregularities
of an increased magnitude as a result of cutting of a yarn.
It is yet another object of the invention to provide an apparatus
for detecting yarn quality information, including compactly
constructed deviation signal emitting units which can be located in
respective association with a number of yarns running parallel and
relatively closely spaced to each other in a yarn production or
processing step and which can provide a continuous movement of yarn
irregularities with as high an accuracy as 1 to 2 percent.
According to the invention, an electrical deviation signal is
continuously derived from a yarn running through a yarn production
or processing step in a manner to correspond with irregularities in
thickness or mass of that yarn. This deviation signal is averaged
over its area to provide an areal average of yarn evenness over the
yarn length. The deviation signal is a also passed to a peak value
detection to provide an average of peak values of yarn evenness
over the length of the yarn. Furthermore abnormally high levels in
the deviation signal which occur isolatedly are detected, thereby
providing detection of fluff or slub of a yarn. Abnormally low
levels in the deviation signal, also occurring isolatedly, are
detected from the low frequency component of the deviation signal,
whereby filament abnormalities in a multi-filament yarn are
detected. Substantial reduction in the rectified output of the
deviation signal is also detected to give an indication of a cut in
the yarn.
The areal average, peak value average and isolatedly detected
abnormal levels of the deviation signal are submitted to overall
evaluation to determine the yarn quality. Areal average detector,
peak value detector and isolatedly occurring abnormal level
detector circuits are shared in a time division scheme by deviation
signals derived from yarns associated with a plurality of spindles.
As a result of above mentioned over-all evaluation, the apparatus
may issue a cutting instruction for cutting a defective yarn at a
given position and interrupting the production or processing of
that defective yarn. The cutting means responsive to such a cutting
instruction is supplied with a deviation signal directly so as to
be controlled additionally in response to a large variation in the
deviation signal that occurs upon cutting of a yarn.
A deviation signal emitting unit provides an electrostatic
conversion of a yarn evenness of a running yarn to be monitored
into an electrical high frequency signal, which is in turn
rectified in a circuit that is relatively free from low frequency
noises. The rectified output is amplified in a negative feedback
amplifier having a low output impedance and capable of providing
cut-off of frequencies below a given value, the resulting output
from the amplifier providing a deviation signal. The deviation
signal is transmitted to a relatively remote position where it is
utilized for detection of averages of areal and peak values and of
the like.
Above and other objects, features and advantages of the invention
will become more apparent from the following description thereof
with reference to the drawings, in which:
FIG. 1 is a system block diagram, partially in circuit diagram, of
an embodiment of the apparatus for detecting yarn quality
information according to the invention.
FIGS. 2A to 2F graphically illustrate wave-form models of typical
examples of a deviation signal,
FIG. 3 shows graphically the relation between the areal average of
yarn evenness and dyeing grade,
FIG. 4 shows graphically the relation between the peak value
average of yarn evenness and dyeing grade,
FIG. 5 shows graphically the relation between the areal average of
yarn evenness and color difference,
FIG. 6 is a circuit diagram of a specific example of a deviation
signal emitting device,
FIG. 7 is a system block diagram of another embodiment of the
apparatus for detecting yarn quality information according to the
invention,
FIG. 8 is a circuit diagram of a specific example of a yarn
cutter,
FIG. 9 is a schematic view illustrating the disposition of a yarn
cutter in a yarn-stretching process, and
FIG. 10 is a circuit diagram of another example of an areal average
detector circuit.
Before proceeding with the description of specific examples of the
invention, it is to be noted that corresponding parts are
designated by like reference characters throughout the
drawings.
Referring to FIG. 1, reference numeral 1 denotes a deviation signal
emitting device through which a yarn 2 to be monitored runs and
which provides an electrical signal indicative of the evenness of
the thickness or mass of the running yarn 2 at an output terminal
3. The electrical signal indicative of yarn evenness or deviation
signal as termed herein is amplified in an amplifier 4 before being
supplied to an areal average detector circuit 5. The amplifier 4
may comprise an operational amplifier, for example, which produces
a null d.c. output when no input is present. Preferably, the areal
average detector circuit 5 should average out the deviation signal
of opposite polarities regardless of the polarities. As an example,
FIG. 1 shows that the output of the amplifier 4 having one polarity
is coupled through a diode 6 to one of the input terminals, 8, of a
differential amplifier with a negative feed back, or an operational
amplifier 7, while the output from the amplifier 4 having the other
polarity is coupled through a diode 9, poled oppositely to the
diode 8, to the other input terminal 10 of the operational
amplifier 7. In this manner, an amplified deviation signal of one
polarity is applied to the input terminal 8 and an amplified
deviation signal of opposite polarity is applied to the input
terminal 10. One of these inputs is reversed in polarity while the
other remains unchanged in polarity, so that the both signals are
rendered to have like polarity for addition. The added output is
averaged by a time constant circuit 13 comprising a resistor 11 and
a capacitor 12. The circuit 13 is chosen to have a time constant
which is greater than the pulse width of long duration pulses
contained in the deviation signal. To give an example, the resistor
11 may have a resistance on the order of 1 megohm and the capacitor
12 may have a capacitance of the order of 2 microfarads for a
deviation signal derived from a monitored yarn 2 of synthetic fiber
travelling through a stretching process with a running speed of 500
to 4,000 meters per minute. However, it will be appreciated that
these figures can vary with the running speed of the yarn 2
monitored. An areal average output derived from the deviation
signal is obtained at the output terminal 14 of the time constant
circuit 13.
The deviation signal from the amplifier 4 is also supplied to a
peak value average detector circuit 15 which preferably comprises a
voltage doubler as shown in FIG. 1. The detector circuit 15 shown
includes a series connection of resistors 16 and 17 having one end
connected to the output of the amplifier 4 and its other end
grounded. The junction between resistors 16 and 17 is connected
through a capacitor 18 and a diode 19 to the ground, with the
junction between the capacitor 18 and diode 19 connected through
another diode 20 and capacitor 21 to the ground. The diodes 19 and
20 are poled so that one diode has its anode connected with the
cathode of the other. The junction between the diode 20 and
capacitor 21 connected to an output terminal 23 through a resistor
22 having a high resistance such as 10 megohms. This arrangement
provides rectified peak values of the deviation signal at the
output terminal 23.
The deviation signal appearing at the input of the amplifier 4 is
supplied to a circuit 24 which is operable to detect abnormally
high levels which occur isolatedly in the deviation signal. In the
example shown, the deviation signal at the input of the amplifier 4
is supplied to the base of a transistor 25 connected in an emitter
follower configuration. The resulting deviation signal obtained as
a low impedance output at its emitter is supplied to a Schmidt
trigger circuit 28 which comprises a pair of transistors 26 and 27.
Though a deviation signal involves a minor fluctuation on the order
of about 1 to 2 percent as referenced to the thickness of a yarn
because of electrical noises and other noises caused by mechanical
vibrations, the Schmidt trigger circuit 28 is arranged such that it
is triggered or switched to the opposite state in response to an
input level which is by more than 10 percent, for example, in
excess of the average level of the normal deviation signal.
Alternatively, in terms of yarn thickness, the Schmidt trigger
circuit 28 is designed to operate when the deviation signal exceeds
the average level by an amount which corresponds to 10 deniers. The
operative level can be established, for example, by adjustment of a
variable resistor 29 connected in the base bias circuit of the
transistor 26. An abnormal high level detection output is obtained
at a terminal 30. It is noted that the deviation signal for the
circuit 24 is supplied from the terminal 3 directly in view of the
high levels that are to be detected by this circuit.
The output from the amplifier 4 is additionally applied to an
amplifier 31 before being supplied to a circuit 32 which is
operable to detect abnormally low levels in the deviation signal
that occur isolatedly. To provide such a low level detection, the
output from the amplifier 31 is passed through a transistor 33,
connected in an emitter follow configuration, to a low pass filter
36 of integrator type constituted by a resistor 34 and a capacitor
35, in order to prevent a minor fluctuation of the deviation signal
from operating the circuit. The filter output is supplied through
an emitter follower transistor 37 to a Schmidt trigger circuit 38.
The polarity of the deviation signal is reversed in either the
amplifier 4 or 31, whereby a detection output is obtained at the
output terminal 39 of the Schmidt trigger circuit 38 when the level
of the deviation signal has fallen below the normal level, e.g., by
10 percent or when the thickness of the yarn has decreased by an
amount corresponding to 1.5 deniers or greater.
The rectified output of the deviation signal, or in the example
shown, the output obtained at the junction between the diode 20 and
capacitor 21 of the peak value detector circuit 15, is supplied to
a yarn cut detector circuit 40 which comprises a Schmidt trigger
circuit.
The deviation signal from the emitting device 1 assumes a number of
waveforms depending upon the kind of yarn evenness. FIG. 2A shows a
relatively close succession of pulses, which corresponds, for
example, to the occurrence of irregularity length or pulse width,
W.sub.1, on the order of 5 cm at an interval, T.sub.1, on the order
of 10 to 30 cm. FIG. 2B shows a wavy variation of relatively large
amplitude, the period T.sub.2 being on the order of 1.5 to 2.0
meters. FIG. 2C illustrates the occurrence of yarn evenness of
relatively large amplitude at a long interval. The length of
irregularity W.sub.2 is about 1.0 to 1.2 meters with interval
T.sub.3 on the order of 8 meters. In this instance, thick and thin
portions may occur in succession as shown in FIG. 2D. In addition,
isolatedly occurring thick or thin irregularity may occur in FIG.
2E or 2F, respectively, such irregularity having a length from 1 to
20 cm or greater.
When there is an irregularity such as shown in FIGS. 2A and 2B, the
areal average detector circuit 5 of FIG. 1 will have an output
which provides an indication of the average value of irregularities
as appearing along the length of a yarn 2 to be monitored. The peak
value average detector circuit 15 detects irregularities which
cause deviation signals depicted in FIGS. 2C and 2D and provides
the average of peak values over the length of the yarn 2 monitored.
When a deviation signal as shown in FIG. 2E is present, the
abnormal high level detector circuit 24 provides an output. Such an
output indicates the presence of isolatedly occurring thick yarn
portions such as fluffs or slubs. For a deviation signal as shown
in FIG. 2F, the abnormal low level detector circuit 32 provides an
output at its output terminal 39, which indicates the presence of
isolatedly occurring yarn irregularity of abnormally reduced
thickness extending over an extent of several centimeters to
several meters, which may be found with a multi-filament yarn as
monofilament abnormality. When the yarn 2 monitored is cut off, the
output from the peak value detector circuit 15 will become null,
thereby actuating the yarn cut detector circuit 40 to provide a
corresponding indication.
In this manner, by the use of the apparatus for detecting yarn
quality information according to the invention, it is possible to
detect the magnitude and discern the kind of irregularities for
determining the yarn quality. It is found that the quality
information obtained with the apparatus of the invention exhibits
good coincidence with the determination of yarn quality that is
obtained by the prior art method of observing dyeing results. This
will be described below with reference to experimental examples. A
yarn 2 being monitored was used to knit a number of cloths, which
were subsequently dyed. Six dyeing grades of dyed cloths were then
determined by visual comparison of these samples with a standard
specimen. Dyeing grade 5 represents complete absence of shading and
dyeing streak, grade 4 includes a slight amount of shading but
without dyeing streak, grade 3 exhibits the presence of a slight
amount of both shading and dyeing streak, grade 2 involves a slight
amount of shading together with an appreciable dyeing streak, grade
1 includes a considerable amount of shading and dyeing streak, and
grade 0 represents the presence of a highly intense shading and
dyeing streak. These dyeing grades are plotted on FIG. 3 as
abscissa against the areal average or the output of the detector
circuit 5 obtained from deviation signals of corresponding yarns as
taken prior to their dyeing, such average values being taken on the
ordinate. The small circles on the graph correspond to yarns which
comprise 24 filaments and are 50 denier thick, while crosses on the
graph correspond to yarns comprising 36 filaments and 75 denier
thick. It is seen that the lower the areal average output, the
better the dyeing grade is rated. It is noted that there is a well
defined correspondence.
The output from the peak value average detector circuit 15 for the
same yarns are plotted on FIG. 4 against the dyeing grade as
abscissa. Again the dyeing grade is improved with reduction in the
output from the circuit 15, and the plotted values establish a well
defined correlation. Then color variation of dyed cloths was
determined, not by visual inspection, but by instrument, and a
difference .DELTA.E from a standard was derived. In FIG. 5, the
difference .DELTA.E is plotted in NBS units on the ordinate against
the areal average output obtained for the deviation signals of
corresponding monitored yarns. The correlation is again well
defined.
An increase of the deviation signal as shown in FIGS. 2A and 2B or
the output from the areal average detector circuit 5 results in the
appearance or increase of shading effect in the corresponding dyed
cloth or the so-called "deep dyed defect." It is found that an
increase of the deviation signal of the type shown in FIGS. 2C and
2D or the output from the peak value average detector circuit 15
results in a dyeing streak in the corresponding dyed cloth.
Thus, with the apparatus for detecting yarn quality information of
the invention, a deviation signal can be derived from a running
yarn monitored during the yarn production or processing step to
yield areal average, peak valve average and the like, all of which
can be utilized to provide an objective, accurate yarn quality
information directly that is comparable to that obtained by the
prior art procedure, while avoiding the troublesome weaving or
knitting of yarn into a cloth, dyeing the cloth and evaluating the
dyeing result involved with the latter. Hence, yarn evenness
information contained in a deviation signal that is derived during
a yarn production or processing step can be supplied to an
electronic computer, for example, to determine the grade of yarn
quality automatically or to control a certain part of the
instrumentation associated with that step thereby enabling an
on-line control to assure an improved and uniform quality of the
yarn. Where such evaluation of yarn quality or process control is
effected, it is preferred that a common apparatus be shared by a
number of yarns running parallel from a number of spindles. To
accomplish this, it is essential that deviation signals derived
from the respective yarns be collected at a single location without
being influenced by noises.
A deviation signal emitting device 1 suitable for use at this end
is shown in FIG. 6. The device 1 includes a high frequency
oscillator 50 which operates in a frequency range from 10 to 50
MHz. The oscillator 50 comprises a single transistor as an active
element which is provided with temperature compensation, and the
allowable collector loss of the transistor is chosen three to five
times the actual loss or greater, with the provision of a
stabilized d.c. power source, thereby assuring a high stability and
low noise oscillator.
The high frequency voltage from the oscillator 50 is applied across
a pair of oppositely located electrode plates 52 and 53 through an
impedance element 51. A yarn 2 to be monitored is threaded between
the electrode plates 52 and 53. It will be appreciated that any
irregularity of yarn 2 will cause a change in the capacitance
across the electrode plates 52 and 53, which change will appear as
a variation of the high frequency voltage across the impedance
element 51.
The high frequency voltage thus obtained across the impedance
element 51 is rectified by a rectifier 54 having little low
frequency noises, which may be a silicon epitaxial diode of planar
type designed for high frequency applications. The rectified output
is applied across a resistor 55 and a capacitor 56 connected in
parallel. It will be understood that any variation or irregularity
of the yarn 2 monitored will appear as a minute voltage change
across the resistor 55. For the stretching step of synthetic
fibers, it is found as a result of extensive experimental work
conducted over years that yarn evenness can be completely known
from measurement of irregularities extending from 1 mm to 100 m
lengthwise of the yarn. For this reason, when the yarn 2 monitored
runs at a speed of 1,000 meters per minute, for example, the
detection of signals having frequencies from about 0.1 Hz to 10 KHz
is sufficient.
Consequently, only irregularity signals within such a necessary
frequency band are amplified in a stable manner. At this end, the
resistor 55 has its one end connected to the ground through a
capacitor 57, and its other end connected with the output and the
inverse polarity input terminal of an operational amplifier 58 that
is formed by a semiconductor integrated circuit and designed for
constant current operation. The other input terminal to which an
input of the same polarity as the output of the amplifier 58 is
applied is connected to the ground by a parallel combination of a
resistor 59 and a series circuit including a resistor 60 and a
capacitor 61. The output terminal of the amplifier 58 is connected
to the ground through a resistor chain including resistors 62, 63
and 64, the junction between the resistors 63 and 64 being
connected through a negative feedback resistor 65 to the inverse
polarity input terminal to provide a high degree of negative
feedback.
The resistors 55 and 60 have a same resistance R, the resistors 59
and 65 have also a same resistance, and the capacitors 57 and 61
have a same capacitance C. So that the lower cut-off frequency f
required for amplification can be as low as a fraction of 1 hertz,
these parameters are chosen to satisfy the relation:
1/(2.pi.R C) = f
In this manner, a highly stabilized high output voltage of high
accuracy can be obtained at the terminal 3 connected to the
junction between the resistors 62 and 63. A low output impedance of
the amplifier 58 makes it immune from the influences of external
noises and makes a long distance transmission of a deviation signal
possible.
In order to allow the yarn 2 being monitored to pass the space
between the electrode plates 52 and 53 freely, the length of the
gap therebetween should be chosen large in relation to the yarn
thickness, e.g., five to more than 10 times the latter. As a
result, the variation in capacitance across the electrode plates 52
and 53 in response to the irregularity of yarn passing therebetween
will be very small. As an example, with a yarn 2 having thickness
of 50 deniers passing between the electrode plates 52 and 53, the
rate of change of the d.c. voltage developed across the resistor 55
is about 10.sup..sup.-5, and hence, to permit a measurement with an
accuracy of 1 percent, the measurement of above voltage change must
be able to be effected with an accuracy of 10.sup..sup.-7. Yarn
evenness can thus be measured with an accuracy of 1 to 2 percent
for yarns having thickness of 20 to 300 deniers or greater, and the
arrangement shown in FIG. 6 develops a deviation signal of such a
high accuracy. When this deviation signal emitting device is
constructed as a semiconductor integrated circuit, the device can
be implemented with such a small overall size of 20 .times. 60
.times. 50 mm.sup.3, for example, so that a separate device can be
located in association with each of a number of yarns at the
position where they run parallel and relatively closely spaced to
each other. The above arrangement permits the stable transmission
of deviation signals from such position to information detection
unit located at a distance of 10 meters or greater therefrom.
Referring to FIG. 7, an embodiment of the invention in which a
common apparatus is used to derive yarn quality information from a
plurality of yarns being monitored. A plurality of deviation signal
emitting devices 1a, 1b, - - - 1n are located at the position where
yarns from a number of spindles run parallel to each other. These
devices 1a, 1b - - - 1n are connected to a plurality of yarn
cutters 70a, 70b - - - 70n, respectively, which will be described
more fully later, and thence to a scanning circuit 72 through a
plurality of transmission lines 71a, 71b - - - 71n, respectively.
The scanning circuit 72 multiplexes deviation signals from the
devices 1a, 1b - - - 1n in sequence and feeds them to a primary
information detection unit 73 which includes the amplifier 4, areal
average detector circuit 5, peak value average detector circuit 15,
abnormal high level detector circuit 24, abnormal low level
detector circuit 32 and yarn cut detector circuit 40 described
previously in connection with FIG. 1. In addition, the primary
information detection unit 73 includes an areal average abnormality
detector circuit 74 which may comprise a Schmidt trigger circuit,
for example, so as to provide a detection output when the output of
the areal average detector circuit 5 exceeds a given value; peak
value average abnormality detector circuit 75 which operates in
response to an output from the peak value average detector circuit
15 exceeding a given value and which may similarly comprise a
Schmidt trigger circuit; an abnormal level detector circuit 76
which may comprise a flip-flop circuit to store any output from
either the abnormal high level detector circuit 24 or abnormal low
level detector circuit 32; a computer access circuit 77 responsive
to an output from the yarn cut detector circuit 40, abnormality
detector circuits 74 and 75 and abnormal level detector circuit 76;
a circuit 79 responsive to a yarn cutting instruction issued by an
electronic computer 78 for developing a yarn cutting signal; and a
storage 80 for storing deviation signals from the amplifier 4 as
required.
The outputs of the areal average detector circuit 5, peak value
average detector circuit 15, yarn cut detector circuit 40 and
abnormal level detector circuit 76 are supplied to corresponding
input circuits of the electronic computer 78 through a group of
switches 81. In this instance, the outputs of both the areal
average detector circuit 5 and the peak value average detector
circuit 15 are connected with analogue-digital conversion circuits
82 and 83, respectively, to supply their output in digital form to
the computer 78.
In operation, assume now that one of the devices 1a, 1b - - - 1n
which may be the device 1a is connected by the scanning circuit 72
to the primary information detection unit 73 for conveying the
deviation signal from the device 1a thereto for a selected time
interval which may be about 10 seconds, for example, in order to
allow detection of various kinds of irregularities. When no
irregularity has been detected, that is, when there is no output
from any of the detector circuits 40, 74, 75 and 76, the scanning
circuit 72 is automatically controlled to advance for connection of
the next device 1b with the primary information detection circuit
73.
On the other hand, when there is an output from any one of the
detector circuits 40, 74, 75 and 76, the access circuit 77 is
operated to drive the computer 78, and a signal therefrom is
applied to a switch control circuit 84 to turn on the switches of
the group 81. Thereupon, outputs from the circuits 5, 15, 40 and 76
are respectively supplied to the computer 78 for information
processing therein in a given manner. Subsequent to such supply of
the outputs, the scanning circuit 72 is controlled by an
instruction from the computer 78 to connect the next device 1b with
the primary information detection circuit 73. In this manner, the
devices 1a, 1b - - - 1n are connected in turn to the primary
information detection unit 73 with a cyclic period of 13 minutes,
for example, thereby achieving substantially continuous storage of
primary information in the computer 78.
The signal to switch over the scanning circuit 72 also closes
normally open switches 85 and 86 connected in parallel with
capacitors 12 and 21, respectively, shown in FIG. 1, thereby
clearing old information stored by the areal average detector
circuit 5 and the peak value average detector circuit 15.
Similarly, the abnormal level detector circuit 76 is reset each
time the scanning circuit 72 is switched over.
The electronic computer 78 is coordinated with the deviation signal
emitting devices 1a, 1b - - - 1n so that the number of occurrences
and the magnitudes of irregularities can be stored in digital form
for each kind of detected irregularities in order to rank the
associated yarns according to the dyeing grade described with
reference to FIGS. 3 to 5, and if desired, irregularities of each
kind can be accorded differential weights to allow summing up the
weighted irregularities for every deviation signal emitting device
or corresponding yarn to provide an over-all estimate thereof for
determining the quality grade. Based on such evaluation, it is
possible to exercise a proper control over selected part of the
production or processing step for each yarn in order to ensure
uniform and excellent yarn quality. If required, a production or
processing step for a particular yarn that has been determined as
defective can be interrupted by feeding a yarn cutting instruction
issued by the computer 78 to a circuit 79 which produces a yarn
cutting signal to be passed through the scanning circuit 72 to one
of the yarn cutters 70a, 70b - - - 70n that is then in electrical
connection with the scanning circuit 72 for operating that
particular yarn cutter to cut the associated yarn.
For effecting such cutting, the supply of the cutting signal may be
through a separate route other than the path of supplying a
deviation signal to the scanning circuit 72, but the both signals
can be conveyed through the same transmission path. Where the
common transmission line is used, the yarn cutter may be utilized
not only to cut the yarn in response to an instruction from the
computer, but also to cut a yarn, once cut spontaneously for some
reason, at a given position and to retain it in order to prevent it
causing additional cutting of other yarns by its cut end entangling
with guide rollers or adjacent running yarns.
FIG. 8 shows an example of such an arrangement. The yarn cutter
includes a resistor 87 of relatively small resistance through which
a deviation signal from a device 1 passes to the primary
information detection unit 73 via transmission path 71. Across the
resistor 87 are connected a pair of oppositely poled diodes 88 and
89 in series, and the junction between the diodes 88 and 89 is
connected to the ground through resistors 90 and 91 connected in
series. The junction between the resistors 90 and 91 is connected
with the gate electrode of a thyristor 92. The thyristor 92 has its
cathode connected to the ground and its anode is connected through
the drive coil 93 of a yarn cutter, a current limiting resistor 94
and a switch 95 in series with a supply terminal 96. The junction
between the drive coil 93 and resistor 94 is connected to the
ground through a capacitor 97. The normal level of a deviation
signal is chosen insufficient to cause conduction through the
diodes 88 and 89.
FIG. 9 schematically illustrates a stretching step wherein it is
noted that a spun yarn bobbin 98 supplies a yarn 2 being monitored
to a first and second stretching rollers 99 and 100 to be wound on
a take-up pirn 101. The yarn cutter 70 is positioned along the path
of yarn from the bobbin 98 immediately adjacent the bobbin 98. The
deviation signal emitting device 1 is located immediately before
the take-up pirn 101.
In the arrangement described above, the deviation signal from the
device 1 is normally passed through the yarn cutter 70 and the
transmission path 71 to the primary information detection unit 73.
Based on the detected information from the unit 73, the computer 78
may issue a yarn cutting instruction, and in response thereto, the
circuit 79 may supply the transmission line 71 with a yarn cutting
signal. The yarn cutting signal is chosen to have an appreciably
high level of several volts, for example, as contrasted to several
hundred millivolts for the level of the deviation signal, so that
when a yarn cutting signal is present, the diode 89 conducts to
provide an actuating signal to the gate of the thyristor 92, which
therefore conducts to energize the drive coil 93 for cutting the
yarn 2 being monitored with the cutter. Since the thyristor, once
conducts, maintains its conductive state, such state of the
thyristor may be utilized to retain the cut end of the yarn, as
left on the supply side, with the cutter itself or by separate
means operated by the thyristor 92. However, such retaining
arrangement is not essential, since the disposition of the yarn
cutter 70 or its electromagnetic blade means immediately adjacent
the bobbin prevents further withdrawal of the yarn so cut. The
resistance of the resistor 87 is chosen less the d.c. impedance of
the negative feedback amplifier 58 within the device 1, as viewed
from the output side thereof, in order to assure positive cutting
operation without the cutting signal being fed to the device 1.
In the above arrangement, when the yarn 2 being monitored happens
to be cut intermediate the stretching process, there will be no
longer a yarn 2 between the electrode plates 52 and 53 of the
device 1 so that the deviation signal will rapidly increase from a
level of several hundred millivolts to a level of several volts in
view of the high degree of negative feedback applied to the
amplifier 58 as shown in FIG. 6. The resulting higher level signal
is applied to the yarn cutter 70 to cause conduction of the diode
88 and hence of the thyristor 92, whereby the yarn 2 being
monitored is cut at its supply end in the similar manner as
mentioned above. Consequently, the possibility that a yarn cut
intermediate its stretching process becomes entangled with rollers
and other yarns to cause additional cutting of the latter is
eliminated.
The areal average detector circuit 5 and the peak value average
detector circuit 15 can be constructed as a full-wave rectifier for
the deviation signal with time constant circuits of relatively
small and large time constants being used for the former and the
latter, respectively. Alternatively, the areal average detector
circuit 5 may be constructed without using an amplifier, as shown
in FIG. 10. Referring to this figure, diodes 105 and 106 serve to
supply a deviation signal of one polarity to a time constant
circuit 111 which comprises resistors 107 and 108 and capacitors
109 and 110, and to supply a deviation signal of the other polarity
to a time constant circuit 116 which comprises resistors 112 and
113 and capacitors 114 and 115. The signals obtained across the
resistors 108 and 113, respectively, are added together with the
same polarity and averaged out by the time constant circuit 13. The
charging time constant determined by the resistor 108 and
capacitors 109 and 110 as well as the charging time constant
determined by the resistor 113 and capacitors 114 and 115 are
chosen several times greater than the pulse widths contained in the
deviation signal by using capacitors of large capacitance. The
discharge time constant determined by a diode 117 connected in
parallel with the resistor 108, resistor 107 and capacitors 109 and
110 as well as the discharge time constant determined by a diode
118 connected in parallel with the resistor 113, resistor 112 and
capacitors 114 and 115 are chosen less than the time interval
between adjacent occurring pulses contained in the deviation
signal. With such an arrangement, positive pulses in the deviation
signal will appear faithfully across the resistor 108, and upon
termination of such pulses, the charge on the capacitors 109 and
110 will be discharged rapidly. In a similar manner, negative
pulses in the deviation signal will appear faithfully across the
resistor 113, and upon termination of such pulses, the charge on
the capacitors 114 and 115 will be discharged rapidly. The pulses
which appear across the resistors 108 and 113 are added together
with the same polarity and averaged out in the time constant
circuit 13 to provide an output which properly corresponds to the
average of area of yarn irregularities over the length of the yarn.
Both arrangements of the areal average detector circuit shown in
FIGS. 1 and 10 provide a faithful detection of the average of area
of irregularities even when the magnitude and the number of
occurrence of irregularities are subject to a great variation.
When the peak value detector circuit of voltage doubler type shown
in FIG. 1 is used as the peak value average detector circuit 15,
there will be obtained an output which, for yarn irregularities
causing a succession of alternately positive and negative pulses as
depicted in FIG. 2D, namely, for a yarn having alternately and
closely located portions of increased and decreased thickness,
represents the sum of the respective amplitudes of the positive and
negative pulses for an improved indication of yarn evenness.
In addition to the deviation signal emitting device 1 shown in FIG.
6, other conventional devices including a device having a pair of
electrode plates connected in one of branches of an a.c. bridge and
disposed for passage of a yarn being monitored therebetween may be
used. The yarn cut detector circuit 40 may be connected with the
areal average detector circuit 5, but its connection with the peak
value average detector circuit 15 assures an improved detection
free from malfunction, since the circuit 15 detect noises generated
during the running of the yarn with an increased sensitivity and
hence an interruption of noises is positively sensed by this
circuit as indicative of a cut in the yarn. While in the above
description, the outputs from detector circuits 24 and 32 which
detect the presence of isolatedly occurring abnormally high and low
levels, respectively, are stored in the abnormal level detector
circuit 76 common to both, they may be stored separately. Also the
disclosure illustrated a single detector circuit 24 to detect
abnormally high levels, a plurality of such circuit may be
provided. For example, by providing two of such circuits, one may
be set to provide an output in response to an increase of the
deviation signal above the average level by an amount corresponding
to 10 deniers, for example, for detecting the presence of
significant fluffs for utilizing such information for the purpose
of quality evaluation and interruption control of the yarn
production or processing step, while the other may be set to
provide an output at a level which is by an amount of 3 to 4
deniers higher than the average level of the deviation signal, thus
detecting smaller fluffs to find failure of yarn contacting members
such as guide rollers or guide plates for their replacement. This
allows an efficient utilization of such yarn contacting members
which heretofore had to be replaced periodically.
While the prior art practice of determining yarn quality required
extracting samples of a yarn, weaving or knitting them into cloths,
dyeing the cloths and visually inspecting the dyed cloths for
ranking the dyeing grade, the above described apparatus for
detecting yarn quality information of the invention eliminates the
need for such troublesome steps by deriving deviation signals from
running yarns and processing the signals to produce various kinds
of yarn evenness information which are totalized to predicate the
yarn quality accurately. This permits immediate evaluation of yarn
quality during yarn production or processing step, thereby enabling
yarns of uniform and excellent quality to be obtained and labor to
be saved.
It should be understood that the apparatus according to the
invention can be applied in industry for determination of
individual yarn qualities such as thickness or mass in various
steps including both melt spinning and wet spinning, stretching and
false twisting steps as well as in any other manufacturing steps
for filamentary or film-shaped products.
While the invention has been described with reference to particular
embodiments thereof, it should be understood that various
modifications and changes are possible to those skilled in the art
without departing from the spirit and scope of the invention.
Therefore, it is intended that the appended claims cover all such
modifications and changes as fall within the scope of the
invention.
* * * * *