GB2023675A

GB2023675A - An apparatus for determining, without contact, the degree of interlacing of a multifilament yarn

Info

Publication number: GB2023675A
Application number: GB7920115A
Authority: GB
Original assignee: Akzo NV
Current assignee: Akzo NV
Priority date: 1978-06-09
Filing date: 1979-06-08
Publication date: 1980-01-03
Also published as: FR2428258B3; ES243828U; JPS54181144U; AT382246B; GB2023675B; CH638316A5; ATA415379A; FR2428258A1; ES243828Y

Abstract

An apparatus for determining the degree of interlacing of a multifilament yarn and particularly the distance between interlacing points does so by inducing static electricity in the yarn so that the filaments separate between interlacing points. The apparatus comprises yarn input mechanism (2); an electrode (4) for connection with a high voltage d.c. source, which has a thread guide eyelet and which is provided with a spark-proof insulator (5) having a thread duct (24); a thread guide (9) connected with earth; a take-off device (10), and an electro-optical device (7, 8) which records interlacing points, arranged in a common housing. The distance between interlacing points is expressed both in analogue form (18) and digital form (19 to 22). The apparatus preferably also comprises an air moistening device (14) for introducing moistered air into the immediate vicinity of the electrode. <IMAGE>

Description

SPECIFICATION An apparatus for determining without contact, the degree of interlacing of a multifilament yarn The present invention relates to an apparatus for determining, without contact, the degree of interlacing of a multifilament yarn which is interlaced by treatment with a jet of compressed gas.

When processing untwisted filament yarns, known interferences generally occur in the thread travel during weaving or during processing on knitting machines and knitting frames. As there is no thread end, breakages of the filament generally lead to thread breakages. Untwisted filament yarns therefore have to have a definite thread end for subsequent processing. Possible methods of providing a definite thread end include, for example, twisting, adhesion between the individual filaments for the duration of the processing treatment by means of a suitable preparation or size, the adhesive being washed out again after processing, and, more recently, a method in which untwisted filament yarns are given a thread end by the so-called interlacing of the filaments.

The thread end which can be achieved by the latter method has been found from experience to be in effect fairly similar twisted yarns, so that interlaced yarns have become increasingly important, particularly since the interlacing treatment can be coupled with other operations. Different interlaced effects are desired, depending upon the application of the yarns. In contrast to twisting, however, the effect actually obtained in the treated yarn cannot clearly be determined by choice of operating parameters. Considerable importance is therefore attached to the monitoring of the treated yarns, particularly since not only the thread end but also other properties such as, for example, handle, volume, lustre and appearance, depend upon the type and intensity of interlacing treatment.

First of all, the terms used in the remainder of the text and in the claims will be defined.

An "interlaced yarn" is a multifilament yarn in which the individual filaments have partially or completely left their parallel orientation and are bound in by friction formed between adjacent filaments at so-called "interlacing points". The filaments run in parallel between the interlacing points.

The term "periodic interlacing" should be interpreted as a form of interlacing in which the multifilament yarn has individual interlacing points which are quite distinct formed in a constant sequence between which the individual filaments run substantially parallel to each other.

"Continuously interlaced" refers to a multifilament yarn which has virtually no clearly marked interlaced points but in which in most cases only a portion of the filaments exhibit completely interlaced points over the entire length.

An "interlacing point" is a point at which several or all the filaments of a yarn are interlaced together and thus exhibit a type of "knot".

The term "opening length" has been adopted as a quantitative description of the intensity of interlacing. It characterises the distance between two adjacent interlacing points. The reciprocal value of the opening length which can occasionally be used is the number of interlacing points per unit length and is designated as the "density of the interlacing points".

Various investigatory methods are known for determining the opening length of a yarn.

For example, the interlacing points of a piece of yarn of defined length are counted in order to determine the opening length. The most widely known method involves determining the opening length with the aid of a needle.

This needle is inserted into a length of yarn subjected to a defined thread tension and is moved along the axis of the thread until it meets an interlacing point. The length over which the needle could be moved freely is measured as the opening length and all the measurements on the length of thread are used to produce an average value, the average opening length. This method is also known as a automated method. The needle at rest is inserted into a filament assembly and the yarn is simultaneously pulled past the needle until the needle meets an interlacing point. As soon as a defined thread tension is reached, the needle is removed from the filament assembly and inserted again immediately downstream of the obstructive knot. The opening length is determined as described above.

All these methods of determining the socalled opening length have considerable disadvantages. Thus, the counting of the interlacing points generally only leads to a useable result without excessive outlay if the interlaced yarns are textured yarns which clearly bulge between the "knots". The examination of the opening length with the aid of a needle which is to be inserted into the yarn denotes considerable interference with the yarn assembly and must lead to falsified results since a minimum of tension will inevitably result in the relative desplacement of the needle, the force of the needle has the effect of reopening the interlacing points which must lead to falsified results. If the yarn has, for example, continuous interlacing, the test result is generally pure chance.It is not possible to obtain a reliable picture of the actual structure of the interlaced yarn.

It has now been found that it is possible to make the structure of an interlaced yarn visi ble and reliably to determine the opening length by making use of the phenomenon which is known per se that multifilament threads which are charged with static electricity spread apart due to the mutual repulsion of like charges on the individual filaments. A technical object of the invention is accordingly to provide an apparatus for determining the interlacing characteristics of a multifilament yarn which allows the type and extent of the interlacing of the yarn to be determined without contact.

According to the present invention there is provided an apparatus for determining, without contact, the degree of interlacing of a multifilament yarn which has been interlaced by treatment with compressed gas, comprising an input mechanism; an electrode for connection with a high voltage d.c. source, which has a thread guide passage or eyelet, and which is provided with a spark-proof insulator having a thread duct; a thread guide connected to earth; a take-off device, and a light barrier which is coupled with evaluating means between the electrode and the thread guide, arranged in a common housing.

The high voltage d.c. source can comprise a suitable transformer, a high voltage cascade and a device for adjusting the operating voltage in the range from about 5 to about 50 kV and can be intergrated in the apparatus.

The input mechanism is preferably joined to a drive motor which can be adjusted smoothly by means of a potentiometer. The delivery rate and therefore the measuring and recording rate can be adjusted in the range of from 0.01 to 10.0 m/min and to 50.0 m/min respectively.

The thread suction device is advantageously a thread suction nozzle which is joined to an air pressure reducing device for super pressures from about 104 to 5 X 105 Nm-2.

In a preferred embodiment of the apparatus according to the invention, the thread duct of the electrode insulator is connected via a connection tube to an air moistening device in order to supply air which is saturated with moisture.

The earthed thread guide is preferably movable. In a particular embodiment, its distance from the electrode can be selected from about 50 to about 500 mm.

The input mechanism with a motor whose speed can be controlled is preferably provided with a thread length measuring device.

The hollow electrode is preferably provided with a spark-proof insulator.

The light barrier is preferably rigidly con nected to a thread length measuring device, a knot counter, an opening length display, an average value display for the opening length, and a recorder.

The thread suction nozzle can be adjusted to take-off effects of from about 0.01 cN/tex to about 0.1 cN/tex or from about 0.1 cN to about 1.0 N. This force effect can be kept substantially constant within very narrow lim its.

The yarn to be examined can be defined precisely within a wide range of variation with respect to its characteristic properties using the apparatus according to the invention. It is passed through a hollow electrode connected to the high voltage source at constant speed.

The value of the voltage can be adjusted smoothly in order to regulate the forces acting on the individual filaments of the yarn accord ingly. In order to make the electric charge of the yarn substantially independent of the preparation used and also of the material of the yarn, it is possible to bring the yarn into contact with air which is saturated with mois ture immediately when charging the yarn with static electricity, this air flowing through the yarn and thus increasing the surface conduc tivity.

Immediately after leaving the electrode, the filament assembly spreads apart on a free length between electrode and an insulated thread guide owing to the repulsion forces of the like charges, the interlacing structure of the yarn becomes visible and allows perfect optical evaluation.

The cooperation of the thread delivery mechanism with the thread suction nozzle, which is charged by means of suitable control divices with compressed air of constant pres sure which can be selected in a wide range has proven to be a very good method of maintaining a constant tensile strength of the thread based on the fineness. Any speed can be adjusted very accurately in the range of the predetermined limits by the electrically driven delivery mechanism which can be regulated very sensitively.

The opening length is determined by the optical scanning of the electro-statically spread yarn with the aid of an electro optical light barrier without touching the yarn. In order to ensure precise centring in the region of the light barrier, the yarn is guided immediately downstream of the scanning region. The en tire scanning system with thread guide is horizontally moveable so that the freely obser vable yarn length can be varied in a range of about 5 to 50 cm. This allows the region of the filament spreading to be selected in such a way that the interlacing characteristic of the yarn being examined at any time can be clearly determined.

The shadow of the beam of light through the spread thread regions and interlacing points, recorded by the light barrier, varies to a surprising extent. Although the thread mass travelling through the ray of light remains constant, it is found that the thread causes quite a different shadow in the portion where it is opened into individual filaments from the portion where interlacing points are present.

Corresponding electric pulses which are de tected, amplified and counted with the aid of an electronic evaluating device are therefore formed at the photodetector. At the same time as the thread length is detected and fed into the counting circuit (by corresponding pulses), the individual values of the opening length can be determined containuously together with the interlacing pulses counted. As soon as the preselected thread length is reached, counting can be stopped automatically, and the number of interlacing points read from the digital counter. It is also possible to select the number of interlacing points to be recorded before-hand and to measure the thread length taken in by the interlacing points (reciprocal value of the opening length).The opening length determined in this way is not sufficient on its own to characterise an interlaced yarn sufficiently with respect to its structure. For this reason, with the apparatus according to the invention it is possible to describe the yarn structure by simultaneous recording of the opening length both as an instantaneous and as an average value, of the standard deviation by the expression of the individual values on a printer or a perforated tape puncher and the analogue representation of the opening length, with the aid of a recorder.

The invention will be descrived in more detail with reference to the accompanying drawings, in which: Figure 1 shows a front view of an embodiment of an apparatus according to the invention.

Figure 2shows a structural diagram of an apparatus according to the invention.

Figure 3, Figure 4 and Figure 5 each show different structures of yarn which has been interlaced by treatment with a compressed gas.

Fig. 1 shows, by way of example, a front view of an embodiment of an apparatus according to the invention. The thread 3 is taken from a supply bobbin 1 (from the left in Fig. 2) with the aid of a delivery mechanism 2 at a constant speed and runs to a suction nozzle 10 supplied with compressed air through a feed pipe 11. From the suction nozzle the thread proceeds with a predeterminable tension through a measuring section, and from the measuring section into a waste container 12 (shown in Fig. 2). A high voltage electrode 4 which is surrounded by an insulator 5 (Fig. 2) is located down-stream of a cover shield 26 which can bear, for example, the type designation. The thread 3 from the delivery mechanism 2 is guided by a small thread guide tube 25 and travels through the high voltage electrode 4 where it is charged electrostatically.The thread spreads apart at the thread outlet 5, of the insulator 5, the interlacing structure which is typical to it being made visible, as shown, by way of example, in Figs. 3 and 5.

The thread structure can be observed through a viewing window 27. A movable thread guide 9 can be moved in the axial direction of the thread in order to change the control length of the thread in the field of the viewing window 27. The precise measured length can be adjusted in this process by means of a scale 29. An electro-optical monitoring device 7, 8 is provided between the insulating member 5 and thread guide 9 or and, in a particular embodiment, is designed as a reflex device in which the light source and photodiode are located in the same housing. The electro optical monitoring device is not visible in Fig. 1.

In order to obtain a surface conductivity in the thread 3 which is as constant as possible, independently of the material to be tested, an air moistening device 14 is installed in the apparatus (Fig. 2) and is supplied with air via a feed pipe 1 6 and joined via an air line 1 5 to the thread duct 24 of the electrode insulator 5. The opening into the thread duct 24 is selected in such a way that the air which is charged with moisture merges into the duct as far as possible in the immediate vicinity of the high voltage electrode 4.

A flow meter 30 for the air moistening device 14, a pressure display 31 and an adjusting button 32 for the air pressure of the suction nozzle 10 are located at the front of the apparatus shown in Fig. 1. Either the number of knots or the thread length to be measured can be adjusted on their own counter 33, depending upon the type of measurement desired. The divice can be changed over in a simple manner for this purpose. The value of the electric voltage connected to the electrode 4 and the delivery rate of the delivery mechanism 2 can be adjusted by two adjusting buttons 34 and 35 respectively.

Display devices for the number of interlacing points, the thread length and the opening length are provided in windows 19, 20 and 21.

As shown in the diagram of the apparatus shown in Fig. 2, in addition to the abovementioned means, the apparatus can have, for example an additional recorder 1 8 and a mini computer 22, the mini computer 22 being used to determine the average value of the opening length and the standard deviation.

The entire electronic counting and control device is preferably combined in a single compact member 1 7.

The functioning of the apparatus is simple and can easily be monitored. The thread taken from the supply bobbin 1 is supplied to the measuring section with the aid of the delivery mechanism 2 and is taken through the measuring section by the thread suction nozzle 10.

The air pressure of the suction nozzle can be sensitively adjusted so that a predetermined tensile strength of thread can be very precisely maintained. From the delivery mech anism 2, the thread 3 passes through the thread duct 24 of the insulator 5 surrounding the high voltage electrode 4 and leaves at the outlet 5,. Immediately after leaving the thread duct 24, the thread bulges in accordance with its interlacing structure, in a manner substantially as shown in any one of Figs. 3 to 5, and the actual interlacing structure can be detected clearly in the display window 27. The electro-optical device 7, 8 is provided at any point along the measuring section in order to record the interlacing points. The different pulses produced by the differing shadows of the photodiode are evaluated by the electronic counting and control device 1 7 and made visible in an analogue (position 1 8) or digital (19 to 22) manner in the recording and display divices 1 8 to 22. The measuring and observation section can be adjusted with the moveable thread guide 9 within predetermined limits.

The rate at which the thread 3 enters the measuring section is determined by means of the adjusting button 35 using means known per se and is controlled, for example with the aid of suitable markings 23 by a suitable device 1 3 such as, for example a proximity switch (Fig. 2).

Claims

1. An apparatus for determining, without contact, the degree of interlacing of a multifilament yarn which has been interlaced by treatment with compressed gas, comprising an input mechanism; an electrode for connection with a high voltage d.c. source, which has a thread guide passage or eyelet and which is provided with a spark-proof insulator having a thread duct; a thread guide connected to earth; a take-off device, and a light barrier which is coupled with evaluating means between the electrode and the thread guide, arranged in a common housing.

2. An apparatus according to claim 1, wherein the high voltage d.c. source is intergrated in the apparatus and comprises a transformer, a high voltage cascade and an adjusting device for operating voltages in the range from about 5 to about 50 kV.

3. An apparatus according to claim 1 or 2, wherein the input mechanism is connected to an electric motor with a speed control device.

4. An apparatus according to any of claims 1 to 3, wherein the take-off apparatus is a thread suction nozzle which is rigidly fixed to an air pressure reducing unit for super pressures of from about 104 to 5.0 X 105 Nm-2.

5. An apparatus according to any of claims 1 to 4, further comprising an air moistening device which is arranged next to the electrode with insulator and a connecting tube into the thread duct of the insulator leads from the air moistening device into the immediate vicinity of the electrode.

6. An apparatus according to any of claims 1 to 5, wherein the thread guide which is connected to earth is movable along the axis of the thread duct and is arranged at a distance of from about 50 to 500 mm from the end of the thread duct.

7. An apparatus according to any of claims 1 to 6, wherein the input mechanism is coupled to a thread length measuring device.

8. An apparatus according to claim 7, wherein the thread lenght measuring device, the light barrier, and the evaluating means comprising a device for counting the interlacing points, an opening length display, an evaluating device for average opening length and standard deviation and a recorder are arranged in cooperation with a control device.

9. An apparatus for determining, without contact, the degree of interlacing of a multifilament yarn substantially as herein described with reference to Fig. 2 with or without reference to Fig. 1 of the accompanying drawings.