GB2143045A

GB2143045A - Checking the unwind-ability of textile threads

Info

Publication number: GB2143045A
Application number: GB08415629A
Authority: GB
Inventors: Michel Buzano; Gilles Dor; Maurice Laurent
Original assignee: Rhone Poulenc Fibres SA
Current assignee: Rhone Poulenc Fibres SA
Priority date: 1983-07-07
Filing date: 1984-06-19
Publication date: 1985-01-30
Also published as: DE3425050A1; BE900112A; JPS61106376A; BR8403444A; IT1174247B; FR2548643B1; FR2548643A1; GB8415629D0; NL8402121A; CH659234A5; IT8421763A0; GB2143045B; ES534097A0; ES8504612A1

Abstract

An apparatus and method for checking the unwindability of textile threads (eg from a bobbin 1) comprises a motorised cylinder 3 for drawing off the thread 2 at a speed controlled and measured by a unit 4, the thread tension being measured by a transducer 5 connected to a tension meter 6. Tension readings are supplied to a comparator totaliser unit 8 which counts the numbers of times a preset tension threshold is exceeded over a series of specified time periods. Results of this analysis are displayed via a printer 9 in the form of histograms. In addition, a continuous record of thread tension is produced by a high speed recorder 7. <IMAGE>

Description

SPECIFICATION Method and apparatus for checking the unwindability of bobbins of textile yarns The present invention relates to a method and apparatus for checking the unwindability of bobbins of textile yarns, particularly for measuring variations of mechanical tension occurring in the yarn.

For a long time producers of endless artificial and synthetic yarns, and also users in the weaving and hosiery industries, have been endeavouring to characterise wound yarn packages in order to define whether a particular wound yarn package is or is not of a quality satisfactory for use or whether, for example, any significant progress is made when parameters are adjusted.

Checking the unwindability of wound packages of flat or textured yarn thus makes it possible, for example, to characterise the package and continuously control product quality.

It has already been proposed to record tension in the form of graphs and to compare the graphs with one another. However, the response time and the inherent inertia of the equipment used permit only an approach to the solution, without a precise reply making it possible to confirm whether or not adjust ments to the production process would be advantageous. At this stage it has been found that the mean value of the unwinding tension was not significant in respect of suitability for use, and that tension peaks recorded on the graph were difficult to turn to account.The shape of a graph permits only the definition of the nature of a transient fault (for example broken strands, cyclical or variable effects due to misadjustment or defects of mechanical parts, etc.) In the use of downstream conversion equipment, such as knitting machines, weaving looms, creels, and the like, it has constantly been found that the parameter important to normal working and the quality of the finished product was essentially the value and the number of the tension peaks. By way of example, the unwindability of fine endless textured threads of a count between 11 dtex/7 strands and 22 dtex/7 strands on a high-speed (1,000 m/min) hosiery machine should not, after the last tension adjustment, lead to tension peaks higher than 2.5 grams; if the peaks are higher, thread breakages will occur and entail the stoppage of the machine.If for example it is considered that the critical threshold value of 22 dtex/7 strands is 2.5 grams and that, as a maximum, one stoppage per 7,000 pairs of tights is tolerated, it can be concluded that the programmed quality selected for the application in question must not lead to more than n peaks per kilogram of material, that is to say n peaks per bobbin.

Just as a top tension to be detected can be defined, it is also possible to define a bottom tension, which will enable product quality to be more satisfactorily selected, with two types of maximum minimum peaks.

The present invention relates to an installation enabling these measures to be taken.

The object of the present invention comprises an installation for checking the unwindability of textile yarns coming, for example, from a yarn support, said apparatus comprising means for measuring the draw-off speed of the yarn, a tension transducer connected to a tensionometer provided with a high speed point recorder and a recorder with a converter for recording and plotting histograms of tension peaks higher than fixed threshold values.

The present application also relates to a method of checking the unwindability of textile yarns, said method comprising the steps of: A) providing an apparatus comprising means for measuring the draw-off speed of the yarn, a cylinder mounted on an adjustable speed motor with a digital display for drawing the yarn of via said measuring means, a tension transducer connected to a tensionmeter provided with a high speed recorder and a recorder with a converter recording and plotting histograms of tension peaks higher than fixed threshold values; B) drawing a yarn off a bobbin using said draw-off cylinder; C) passing the yarn through said tension transducer; D) preadjusting the mechanical tension threshold;; E) measuring the variations of the voltage supplied by the transducer and translating the variations of mechanical tension in the course of unwinding of the yarn each defect detected in accordance with the preadjustment of the mechanical tension thresholds being counted in a partial counter in said recorder to give the number of defects during the selected measurement time and also counting in a totalising counter in said recorder and F) plotting the resulting readings on a histogram.

In order that the invention will more readily be understood, the following description is given, merely by way of example, reference being made to the accompanying drawings, in which: Figure 1 is a schematic view of one embodiment of apparatus according to the invention; and Figure 2a, 2b and 2c are histograms produced by the apparatus of Figure 1.

The yarn is drawn off at a constant or non-constant speed, depending on the measurement made.

By recording in graph form the number of tension variations which went beyond the selected thresholds and their spacing on the bobbin, a simple means is thus obtained for effectively controlling and judging quality.

The apparatus illustrated in Figure 1 includes a bobbin, from which a yarn 2 is drawn-off by a cylinder 3, controlled by a speed regulator 4. The yarn passes over a read head 5, which is connected to a tensiometer 6, associated with a high-speed recorder 7, a converter 8 and a convential or typewritertype recorder 9 producing historgrams.

During operation, the yarn 2 is drawn off the bobbin 1 by means of a draw-off cylinder 3 mounted on an adjustable speed motor controlled by a regulator 4 with digital display of speed in metres per minute (speed range 0 to 1,700 m/min). Atension transducer 5 of the Tensotron type (ROTSCHILD Company) is placed upstream of the draw-off cylinder. This transducer is connected to a tensiometer 6, which is coupled to a high-speed recorder 7, to a converter 8 and to a histogram plotter 9. The sensitivity and zero offset of the signal translating the tension are fixed on the tensiometer, and the tensiometer signal is stored in the converter 8 for the plotting of the histogram by the recorder 9.The acceptable limit tension values are displayed on the converter 8 (critical tension thresholds), on the basis of which any tension peak higher than the critical thresholds displayed brings about the transmission of a pulse to the counters of the converter 8. These signals are totalised over a predetermined period of time of between 1 second and 99 minutes. The sum of the signals is transcribed in the form of a line of a length corresponding to the scale selected. The plot having been made, the paper advances one step every three measurements, and is again ready to record the new sum of pulses totalised in the next unit of time; at the same time, each pulse is totalised in the corresponding totalising counter.

If these installations are equipped with a safety device stopping them in the event of the breakage of the thread, they can operate without supervision.

Moreover, they may be provided with a device enabling tension recordings to be programmed on the high-speed recorder, This programming can be effected with a constant time (hour/minute) for a defined period of time (minute/second) (for example hourly for 10 seconds), or when the sum of the tension peaks totalised in one of the categories is above a certain value (which corresponds to an abnormal passage on the bobbin tested, for example).

This principle makes it possible to ensure that information is not lost and that the shape of the curve will indicate whether a broken strand or the passage of a lease, for example, is involved.

As an example, an apparatus was prepared in the following manner, comprising: - An electronic cabinet containing the control mod u.es of the high-speed recorder, the automatic control module of the unwinding system, the controls of the printer, the microprocessors directing these functions, and the control console making it possible to define the parameters of the test and the mode of functioning of the installation.

- A printer (such as the MICROLINE 80 brand), parallel input type, serves as a two-way graph recorder and digital recorder for parameters relating to the previous test.

The electrical characteristics are as follows: - Supply: 220, volts, 6 amperes 50-60Hz - 2 inputs: 1 analog input, 1 logic input - 2 uncontrolled outputs, 220 volts alternating current, 1 ampere - 2 controlled outputs (all-or-nothing control), 220 volts alternating current, 2 amperes, static switch with zero start - 1 controlled output (all-or-nothing control) adapted to break 24 volts direct current, 2 amperes - 1 8-bit output line (TTL logic) - 1 analog output - 1 control console Analog input: -scale 0 to 12 volts peak; Z = 5 K. This input may optionally have a different scale. This input is intended to receive the signal from the tension transducer.

All-or-nothing input: of the TTL type; this input is intended to receive the contact of the thread presence transducer (contact opened by the presence of the thread) free from any external tension.

220 volt 1 ampere uncontrolled outputs: - 1 output is intended for supplying the amplifier of the tension transducer.

- 1 output is intended for supplying the parallel input semi-graphic printer.

220 volt2 ampere controlled outputs: - 1 output serves to supply the unwinding speed control cabinet.

- 1 output serves to supply the high-speed recorder.

24 volt direct current2 ampere controlled output: This output serves to control the marker of the high-speed recorder.

8-bit TTL outputline.

This output line controls the printer.

Analog output: This output enables the tension transducer signal to be applied to the high-speed recorder.

The control console is made up as follows: - "Functions": 2 encoder wheels enable the number of the desired function to be selected (function mode and parameters to be initialised or displayed).

- "Values": 4 encoder wheels enable the test parameter values to be initialised.

- "Display": - 6 digital light emitting diode displays enable the value of the parameters to be displayed.

- 8 miniature light emitting diode control lights indicate the function mode which has been selected.

- 3 red control lights indicate the type of alarm encountered.

- 1 yellow control light indicates tensions exceeding the upper threshold (major faults).

- 1 green control light indicates tensions exceeding the lower threshold (minor faults).

- "Write": the pushbutton serves to write into the memory of the installation the value of each parameter or the function mode selected.

- "Acquit": the pushbutton serves to stop an acoustic warning device.

During operation, the analog tension applied to the input of the installation (scale 0 to 12 V) is divided and filtered to give a scale of 0 to 9.99 Vat the output of the amplifier stage, and is then compared with the thresholds, whose scale isO to 999. When this value thus divided is higher than the "minorfaults" threshold value (minor fault sensitivity), the green minor fault LED control light lights up, and if the value is lowerthan the "major faults" threshold (major fault sensitivity) a pulse is counted in the "minor faults" counters. If the value is higher than the major fault threshold, the yellow LED control light lights up and a pulse is counted in the "major faults" counters.

Each fault in a given category is counted in a totalising counter and in a partial counter. The totalising or cumulative counter therefore gives the total number of faults recorded in the corresponding category, and the partial counter gives the number of faults recorded in this category during the time of this measurement. The partial counter gives the amplitude of the histogram for the corresponding measurement. At the end of each measurement, it is automatically reset to zero and starts again to count automatically the faults occurring during the next measurement, which is started automatically.

Distribution of functions.

Parameters: functions zero to 22 and 32,33.

Apparatus used: functions 23 to 25.

Function mode: functions 27 to 31.

Zero offset on histogram: function 26.

Initialisation of "exemplified"installation.

When voltage is applied, all the values of the parameters of the test are at zero, none of the mode functions is in use, and the static switches controlling unwinding and the high-speed recorder are open. The value indicated on the displays corresponds to the value of the memory containing the value of the parameter selected by the "functions" encoder wheels. The "write" pushbutton serves to transfer to the memory, in accordance with the parameter defined by the "functions" encoder wheels, the value displayed by the "values" encoder wheels.

After the parameters of the test have been initialised, the function mode of the installation is selected.

Function Mode. The functions 23 to 26 must be combined with one of the functions 27 to 31.

- Function 23: The apparatus serves to totalise the major faults on the one hand, and the minor faults on the other. The high-speed recorder and the printer are not operated.

- Function 24: Function identical to function 23 except for the high-speed recorder, which will be put into operation every time the period of time defined by function 8 has elapsed, the recording time being equal to the value of function 9.

- Function 25: In this function mode the totalisers, the high-speed recorder and the printer will be in operation.

- Function 26: The maximum amplitude of the histogram is 100 points. If the value of the partial counter exceeds 100 in the course of a measurement, two cases may arise: First case: The histogram will indicate the maximum value. In this case, the system will work without scale shift, and therefore function 26 will be initialised with the value 00.

Second case: The histogram will indicate the excess value. In this case, the system will work with a scale shift and the function 26 will be initialised with the value 01, and on the left of the recording will be indicated the number of hundreds of the shift (0 to 9) and the histogram will represent the amplitude of the excess in relation to the number of hundreds registered as the shift.

- Function 27: This function mode permits the unwinding operation if a thread is present and operates the "no thread" alarm and the horn and stops the unwinding if there is no thread at the detector.

Counting of faults can be effected: If function 24 or 25 is validated, the triggering of the high-speed recorder will be controlled solely by the position of the high-speed recorder "on" switch. If function 25 is validated, the printer will be operated and will print the table of the parameter values before permitting the unwinding of the thread. The parameters can be modified at any time in this function mode.

- Function 28: This function mode is identical to function mode 27, but in addition the recorder is triggered by the recording time base, or the limits defined in functions 10 and 11, and the apparatus controls the different thresholds and limits of certain functions. Moreover, the parameters cannot be modified in the course of this function.

On passing from function 27 to function 28, the counters are reset to zero, the time bases are re-initialised and the printer records the parameters of the test and their values. Measurements then start.

- Function 29. This function makes it possible to modify one or more parameters during the course of function 28. When this function is enabled, permission to perform the unwinding operation is suspended; this also applies to the triggering of the high-speed recorder. After modification of the parameters, function 30 ("restart") is enabled in order to be able to continue the test with the new parameters.

- Function 30: At the commencement of this function the printer, if in operation, records all the parameters and their values in order to show the changes of parameters which have been made, the recording of the histogram and the controls of thresholds and limits taking place as in function 28.

- Function 31: This function cancels the authorisation to effect the unwinding and to operate the recorder, resets the counters to zero after having printed the cumulative totals, increments the test number counter and positions the apparatus for the analysis, for example, of a new bobbin, while retaining the parameter values of the preceding test.

The semi-graphic printer used makes it possible to plot three cycles of the histogram on each line.

Consequently, a histogram plot made by the printer will correspond to three measurements.

The apparatus makes it possible to check every bobbin of thread. It may also be installed on a conversion machine disposed downstream for the purpose of making the measurements on the moving thread.

The apparatus makes it possible to check any phenomenon which gives rise to variations of mechanical tension which can be translated into variations of voltage.

Independently of its use in the textile industry, the use of this apparatus in medicine, etc. could be contemplated.

The following example illustrates the present invention without limiting it.

Example.

It is desired to measure defects in an endless polyethylene terephthalate thread of a count of 50 dtexl40 strands. The apparatus described above is used with adjustments such that the thresholds of sensitivity to minimum and maximum faults will be respectively unwinding tensions of 3 g and 3.5 g.

These conditions are measured with unwinding at a speed of 500 m/min; 819 majorfaults and 3,064 minorfaults are then found (diagram Figure 2a).

Modifications of adjustment of the density of the wound package and of pattern breaking in the texturing machine are then made. The thread is again unwound at 500 mimic in orderto check the influence of the adjustments: no more faults are then found (diagram Figure 2b). Unwinding then proceeds at a higher speed, starting from which excess tension faults will be seen to occur again.

In this example, it is found that excess tension faults start to appear again at an unwinding speed of 800 m/min (diagram Figure 2c).

This procedure made it possible to classify the bobbins produced in such a manner as to deliver to customers only those bobbins which, in accordance with the application sought here, did not require passage under tension higher than 3.5 g or lower than 3 g, thus having good characteristics making it possible for barring phenomena and differences in appearance or dyeing affinity in the finished article to be avoided.

The accompanying histograms 2a, 2b and 2c are obtained in the following manner. Recordings are made every hour (automatic start) for 1 minute; sensitivity to majorfaults is set at 3.5 g and sensitivity to minor faults at 3 g; tension scale on the ROTSCHI LD apparatus: 10; the thresholds for the recording of the number of major and minorfaults are set respectively at 50 and 300; as soon as these thresholds are reached during unwinding, the operation is stopped automatically and a visual and acoustic alarm is triggered when they are repetitive.

The installation of the present invention thus provides an improvement in the sense that it permits, in a relatively simple manner, the checking of the quality of the threads to be tested in dependence on their use.

Claims

1. Apparatus for checking the unwindability of textile yarns coming, for example, from a yarn support said apparatus comprising means for measuring the draw off speed of the yarn and a tension transducer connected to a tensionometer provided with a high speed point recorder, a recorderwith a converter for recording and plotting histograms of tension peaks higher than fixed threshold values.

2. Apparatus as claimed in claim 1 wherein said means of drawing-off a yarn comprise a cylinder mounted on an adjustable speed motor with a digital speed display.

3. Apparatus as claimed in claim 1, or 2, wherein said recorder further comprises a partial counter for counting defects above said threshold value and a totalising counter for counting the total defects recorded during a selected measurement time.

4. A method of checking the unwindability of textile yarns, said method comprising the steps of: A) providing an apparatus comprising means for measuring the draw-off speed of the yarn, a cylinder mounted on an adjustable speed motor with a digital display for drawing the yarn of via said measuring means, a tension transducer connected to a tensionometer provided with a high speed recorder and a recorder with a converter recording and plotting histograms of tension peaks higher than fixed threshold values; B) drawing a yarn off a bobbin using said draw-off cylinder; C) passing the yarn through said tension transducer; D) preadjusting the mechanical tension threshold; ; E) measuring the variation of the voltage supplied by the transducer and translating the variations of mechanical tension in the course of unwinding of the yarn each defect detected in accordance with the preadjustment of the mechanical tension thresholds being counted in a partial counter in said recorder to give the number of defects recorded during the selected measurement time and also counting in a totalising counter in said recorder and F). plotting the resulting readings on a histogram.

5. Apparatus for checking the unwindability of textile yarns substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

6. A method of checking the unwindability of textile yarns from a bobbin, said method being substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.