US3187568A

US3187568A - Filament fault detector

Info

Publication number: US3187568A
Application number: US95370A
Authority: US
Inventors: Gonsalves Victor Emanuel; Hilferink Garrit Johannes
Original assignee: American Enka Corp
Current assignee: Akzona Inc
Priority date: 1960-03-15
Filing date: 1961-03-13
Publication date: 1965-06-08
Anticipated expiration: 1982-06-08
Also published as: GB906237A; CH387335A; DE1869571U; ES265737A1; ES265739A1

Description

June 8, 1965 v. E. GONSALVES ETAL 3,187,563

FILAMENT FAULT DETECTOR Filed March 13, 1961 INVENTORS VICTOR EMANUEL GONSALVES GARRIT JOHANNES HILFERINK BY A ORBl;

United States Patent 24 6 9 Claims. (Cl. 73-160) This invention relates to the preparation of packages of yarn comprising continuous filaments having a basis of a synthetic material. This invention further relates to a method of and apparatus for signalling and registering the presence of slubs on a running yarn or sheet of yarns.

In the textile industry, thebulk of the so-called semi or fully synthetic continuous yarns produced are supplied to converters in the form of packages for processing into warp beams on Warping machines for use in the weaving and knitting of fabric webs, and also for processing on other yarn holders such as pirns, bobbins, etc. In order to ascertain the final quality of the fabric woven or knitted from said yarns, it is of great importance to know to what degree the yarn as delivered on the packages is slubby.

In synthetic continuous filament yarn slubs are produced in the yarn mainly by the breakage of filaments. Where the broken ends project from the yarn slubs will normally form. The number of slubs. present in a certain length of yarn is in the main a measure of the processibility of the yarn. I

It is well known to employ certain scanning devices to obtain an estimate of the number of slubs in a sheet of yarns being wound onto a warp beam during a warping Operation. In this way the quality of the yarn can be evaluated without this making it possible, however, to improve the qualtity of the final fabric. An investigation of the problem has shown that the majority of slubs estab lished in a woven or knited fabric are present in a small proportion of the total number of yarn threads of which said product is composed. The result of said investigation has led to the fresh insight on which the present invention is based.

An object of the present invention is to provide a system for indicating, signaling and/ or registering the existence of slubs present on a running length of yarn or sheet of yarns.

Another object of this invention is to provide an apparatus for detecting broken filaments or slubs projecting from running yarn or sheet of yarns without engagement therewith.

Still another object of this invention is to provide a system for detecting broken filaments on traveling yarn which does not require frictional engagement between the yarn and detecting means.

Other objects will appear from the following detailed description.

The present invention makes it possible to realize considerable improvements in the qualtity of woven or knitted fabrics in a surprisingly simple manner.

In accordance with this invention each yarn package is provided with an indication of the number of slubs incorporated in the package during winding. Accordingly, the yarn packages to be placed on the creel of a warping or knitting machine can easily be classified according to the number of slubs. Consequently, the amount of first quality product finally obtained increases with startingly rapid progress. Moreover, it has been found possible to trace yarn packages containing many slubs to their source. As a result, an improvement has been obtained in establishing faulty machine operation responsible for the occurrence of said slubs.

To enable the manufacture of yarn packages of the "ice above-described type to be carried out, there has been devised a method for signalling and/ or registering the existence of 'slu'bs on a running yarn or sheet of yarn, which is guided over two thread guides with the aid of a transport device. In a known method of signalling the existence of slubs on a running sheet of yarn, a sheet of yarns is disposed in the shadow of a narrow obstruction intercepting a beam of light which is arranged at right angles with and in the plane of said sheet of yarn. On the side of the sheet of yarn away from the source of light there is a photocell. When a slub passes the light source, it will project beyond the path of the shadow and excite a signal in the photo-cell, which signal is thereupon amplified and registered.

This method is objectionable in that it becomes extremely costly when applied to a single running thread. Moreover, the apparatus required for this purpose comprises equipment, such as the photo-cell and the light source, which is very fragile as well as liable to become obsolete, besides increasing the operating costs. Another objection is the large space required to accommodate such apparatus.

The aforementioned drawbacks are not found in carrying out the method according to the invention, wherein the yarn or the sheet of yarn is passed over a short distance along one or more scanning members consisting of material of electrical conductivity, said devices being positioned between the thread guides and adapted to pass on an electric signal transmitted thereto or induced therein to a device for the electronic amplification and the signalling and/ or registration of the existence of this signal.

Although this method is applicable to a sheet of yarn, it has been found to be particularly advantageous when applied to a single running thread of yarn.

' In the interest of clarity, it is pointed out that a running yarn of a synthetic material is brought to a certain contact potential. Since the material of the yarn possesses practically all the properties necessary for properly insulating electric charges, the yarn retains the electrostatic charge with which it has been furnished. This characteristic holds for a slub on the yarn so that slub too is charged in brushing the thread guides and retains the charge for a substantially long time.

In accordance with this invention a passing slub, i.e. a slub on a running yarn, is detected by means of the electrostatic charge present on the said slub. To this end scanning members of a scanning device are placed so close to the running yarn that a projecting slub passes very closely along one or more of said members, or even brushes them. As a result, the scanning device is furnished with a charge of the same sign as the charge of the slub, thus creating a voltage impulse of the same sign each time the slub passes the scanning device. The voltage impulse, after it has been appropriately amplified, is fed to a signalling and/ or registering means. The apparatus for signalling and/ or registering the existence of slubs on a running textile material comprises means for moving the textile material, two thread guides for guiding the textile material along a fixed path, and one or more scanning members of a material of electrical conductivity in one plane between the guides and at a short distance from the path of the running textile material. The scanning members may be connected individually or in a group or groups to one or more electronic amplifiers, the outputs of which are connected to one or more signalling and/ or registering instruments.

The nature of the signalling and/ or registering instruments may vary greatly. The signalling instrument may be, for instance, a bell, a siren, or a lamp, which is energized when a passing slub has induced an electric signal into one or more of the scanning members. The said instruments may also be connected to a stop motion, which discontinues the movement of the textile material. a

While the apparatus may be employed for detecting the passing of slubs present in a sheet of yarn, as in the form of a warp, thebest results will be obtained where the apparatus according to the invention is used for counting the slubs on a single running thread of yarn, and will be so described. By counting may also be understood here the signalling and/or registering of the passing of slubs, if any, per unit of time or length of the textile material.

The probability of a slub transmitting a signal is greatest where, according to the invention, the scanning'device or devices are arranged symmetrical in relation to the axis of the path of the yarn. If a single scanning device is employed, it should preferably be circular.

Practice has shown, however, that there are various factors which may influence the signalling operation unfavorably or even prevent the passing of a slub from being signalled at all. Thus, it has been found that the electrostatic charge is very unequally distributed over the passing yarn. The nature of said unequal charge distribution is twofold. In the first place the total charge displaces very irregularly along the yarn, as a result of which a very irregularly shaped signal is simultaneously induced into all the scanning members provided. It has not been found possible to separate this signal from that received from a passing slub by means of frequency sitters.

The electrostatic charge may also be distributed unequally over any cross-section of the thread of yarn. This results in an irregular arrangement in relation to the yarn path of the equipotential surfaces effected by the electrostatic charge. If this irregular arrangement of said equipotential surfaces varies very rapidly'and irregularly along the yarn axis, which will always happen, then the yarn itself will excite varying induction voltages in the scanning members.

Surprisingly, it has been found possible to avoid the above drawbacks if, according to the invention, an even number of scanning members, located at an equal distance from the axis of the yarn path, is divided into two equally large interconnected groups which are each connected to an amplifier whose outputs are so connected to a third amplifier that the latter responds only to the differencesignal from the two first-mentioned amplifiers, the output of the third amplifier being also connected to a counting unit. This can be realized, for instance, by connecting the outputs of the two first-mentioned amplifiers to the ends of the primary winding of a transformer, the secondary winding of which is connected to the said third amplifier. However, it is preferable to make use of a wiring system in which the output of one of the first two amplifiers is connected to the output of a reversal stage, the input of which is connected to the output of the other amplifier, the output of the first amplifier being also connected to a counting unit by way of a third amplifier- Variations in the charge along the axis of the yarn that are a result of those charges on the yarn, which give rise to concentric axial-symmetrical equipotential surfaces, will induce equal variations in the charge into the two groups of scanning members, By mixing the amplified signals after the signal received from one of said groups has been converted such variations in the charge can be separated by sifting. The chance of a slub passing the scanning members in such a way that it excites a perfectly identical signal is neglectably small.

If the two groups of scanning members each comprise several scanning members that are so arranged that two of these members, each belonging to a different group, are always placed close together, the effect of the electrostatic potential planes being arranged irregulariy can be practically neutralized without causing interference with the signal received from a passing slub.

Preferably an arrangement is applied in which the scanning members of the two groups are arranged alternately in a star-shaped pattern. This arrangement has been found to be the best possible means of avoiding unfavorable effects on the signals received from slubs. In order to realize this arrangement it is conceivable that straight scanning devices may be inserted over equally long disstances in a ring of insulating material through the center of which the yarn is adapted to run.

According to the invention, however, a very simple solution can be obtained when a construction is used in which the two groups of scanning members are formed by two metal wires wound hclically, the helices being bent into. the form of a circle at an intervals of half a pitch. This construction offers several advantages. Thus, the connections between the scanning members in a group become very short. Moreover, the helical arrangement of the metal wires renders it more probable for the slub to come into contact with one of the helices.

The above arrangement of the scanning members in which two of said devices, each belonging to a different group, e always placed close together is also objectionable in that it causes neighboring scanning members to form a condenser the capacity of which attenuate the intensity of the difierence signal considerably. According to the invent-ion, however, this disadvantage can be avoided by providing each scanning member with one or more screening conductors. Where the scanning members are designed in the above-described shape of helically wound metal wires, the screening arrangement according to the invention can be realized very conveniently by winding one or more insulated metal wires between the helices of the scanning members, the metal wires having the same helices as the scanning members and serving as screening conductors.

In order to transmit a signal of the highest possible intensity to the amplifiers, it has been found necessary according to the invention for the scanning members to be of a very low self-capacity. A satisfactory embodiment of the amplifiers to which the scanning members are connected is characterized by a high input impedance and a low output impedance, whereby the relaxation period of an incoming signal determined by the input impedance and the capacity of the scanning members is at least as long as the period necessary for a slub to pass the scanning device under normal operating conditions.

[For the purpose of explaining the term relaxation period of an incoming signal it is pointed out that the signal may be considered to be fed to an equivalent circuit of the amplifier input. This equivalent circuit consists of a simple R-C (resistance-capacitance) wiring system. Of such a system itis known that a voltage signal dies away in it proportional to the function After a time t=R.C., the so-called relaxation time, the signal is reduced by a factor 1/ e.

It is desirable that the said relaxation time is at least as long as the time taken by a slub to pass the scanning member under normal operating conditions. In this manner the charge of a passing slub is caused to bring about the greatest possible induct-ion charge on the amplifier input.

In the case of a wiring arrangement allowing of a very satisfactory and interference-free amplification of the signals received, each scanning device or group of scanning devices is connected, as a cathode follower, to the grid of an amplifying valve. Each scanning member is provided on both sides with screening members, which are each or by groups connected to the cathode of the amplifying valve whose grid is coupled to the scanning member provided with said screening members.

The above-described apparatus for signalling and registering the existence of slubs on a running yarn or sheet of yarns may be fitted on or form part of many different textile machines, such as creels, winders, and coners.

This apparatus has proved to be of particular advantage in combination with drawtwisters for drawing yarns manufactured from thermoplastic linear polymers such as, for example, polyamides, polyesters, polymethanes and copolymers, since it has been found that the majority of slubs are obtained when the production process of such yarns is in the drawing stage.

If the number of slubs can be determined immediately after drawing and prior to winding, the yarns wound to packages can be sorted in a simple manner. It has been found that the number of slubs that may have been produced after counting, e.g. during winding or other additional treatments is negligibly small. Consequently, they no longer have any essential influence on the quality of the end product.

In order that the invention may be more clearly understood therefollows below, with reference to the accompanying drawings, a description of a drawtwister provided with a scanning device according to the invention.

In the drawings,

FIGURE 1 is a diagrammatic front View of a drawtwister showing a scanning member in position,

FIGURE 2 is a detail View of a scanning member,

FIGURE 3 is a diagrammatic view of the circuit for the amplification of the signals received, and

FIGURE 4- is a detailed diagrammatic representation of the introduction into the amplifier circuit of a received signal.

Like reference characters indicate like parts throughout the several views of the drawings.

In FIGURE 1 the reference numeral 1 indicates a package of undrawn yarn. After this yarn has been drawn down, it is Wound onto another package 2 mount ed on a conventional twisting spindle (not shown). To this end the undrawn yarn 3 runs from the package 1 through a guiding eyelet 4 to a pair of feed rollers 5 and 6. From there it is pulled over the draw pins 7 and 8 by a draw godet 9. After passing the draw pins 7 and- 8, the yarn 3 is wound a few times around the draw godet 9 and the guiding roller 19 and subsequently fed to the twisting spindle, through an eyelet 11, thus forming a yarn balloon 12 with the aid of a traveller 13 of the twisting device and is wound onto the package 2.

Between the draw godet 9 and the eyelet 11 there are provided two thread guides 14 and 15, which keep the yarn 3 very accurately in a fixed path. Also between said two thread guides 14 and 15 there is a scanning member or feeler 1d, repersented in detail on an enlarged scale in FIGURE 2. The feeler consists of a ring 17 of insulating material. The ring 17 is provided with an aperture 18, through which a yarn 3 can be guided intothe ring. The ring 17 is attached to a holder 19 by means of which the feeler 16 can be conveniently mounted in desired position. The arrangement of the thread guides 14 and 15 relative to the feeler 16 is such that a yarn 3, which is led along the

guides

14 and 15, passes through the center of the ring 17.

Around the ring 17, six

metal wires

29, 21, 22, 23, 24 and 25 are wound a few times according to a helical pattern. The

wires

21 and 24. are of bright copper, the others of enameled copper. The wires around the ring 17 are all coated with a very thin layer of plastic material to prevent the ring from becoming dirty. The wires and 22 as well as the

wires

23 and 25 are connected in pairs and function as shielding wires.

FIGURE 2 shows a diagrammatic cross-section of a yarn thread with one broken single filament 26. As will be seen, the so-called slub is obviously nearer to the metal wire windings than the unbroken filaments. Accordingly, the slub in passing through the ring 17 will induce a charge on one winding of the

wires

21 or 24.

From the feeler 16 the signals, received either by the wire 21 or the wire 24, are fed to the identical amplifiers A or A respectively, to which the wires are operatively connected, as shown in FZGURE 3. The amplifiers 5 A and A are cathode followers and function as impedance transformers, i.e. their input impedance is very high and their output impedance low.

Connected in series with the amplifier A is a reversal stage R which efiects a completely uniform reversal of the output signal from the amplifier A Since the output impedance of the amplifiers A and A is low, it is possible for the following circuit elements to be connected to said amplifiers by means of comparatively long cables and be disposed elsewhere.

The output signal from the reversal stage R is mixed with that from the amplifier A As a result, all the noise signals produced by the slubs can be practically eliminated. Moreover, it has been found that the wiring system is highly insensitive to external interferences. All signals measured are subsequently transmitted to an amplifier stage A and from there they are finally passed to a counting unit C. This counting unit C responds in such a way that if two ends of a broken single filament pass, only one slub is counted.

The shielding

wires

20, 22, 23 and 25 are connected to the amplifier stages A and A as is shown in FIGURE 4.

It is to be understood that the foregoing detailed description is given merely by way of illustration and that many variations may be made therein without departing from the spirit of this invention.

What is claimed is:

1. Apparatus for signalling the existence of slubs in a travelling yarn comprising means for drawing the yarn whereby an electrostatic charge is placed thereon, two thread guides for maintaining the travelling yarn in a fixed path, a scanning device positioned along the path of the travelling yarn between the said thread guides and symmetrical in relation to the yarn path, said scanning device comprising an even number of scanning members of electrically conductive material to which the electrostatic charge on the slubs in the textile material is transmitted, said scanning members being located at an equal distance from the axis of the yarn' path and being divided into first and second groups containing the same number of scanning members, first and second amplifiers connected to said first and second scanning groups respectively, a third amplifier to which the outputs of the two said amplifiers are connected in such a manner that only the differencesignal from the two said amplifiers is responded to by said third amplifier, and means connected to the output of said third amplifier for signalling the presence of slubs.

2. An apparatus according to claim 1, characterized in that the output of said second amplifier is connected to the input of a reversal stage, the output of which is connected to the output of said first amplifier, the output of said first amplifier being connected to the signalling means by way of said third amplifier.

3. An apparatus according to claim 1, characterized in that the groups of scanning members are formed by two metal wires wound helically and at an interval of half a pitch, the helices being bent into the form of a circle.

4. An apparatus according to claim 1, characterized in that the scanning members are insulated from each other by one or more shielding conductors.

5. An apparatus according to claim 3, characterized in that between the helices of the scanning members insulated metal wires are wound of the same helices as that of the scanning members, the metal wires serving as screening conductors.

6. An apparatus according to claim 5, characterized in that the scanning members have a very low self-capacity.

7. An apparatus according to claim 1, characterized in that the amplifiers to which the scanning members are connected have a high input impedance and a low output impedance, whereby the relaxation time of an incoming signal determined by the input impedance and the capacity of the scanning members, is at least as long as the time necessary for a slub to pass the scanning member under normal operating conditions.

8. An apparatus according to claim 1, characterized in that a plurality of scanning devices are employed and the scanning members of said'scanning devices are connected to the grids of the amplifying valve of the amplifier, said amplifying valves being connected as a cathode follower, and each scanning device being provided on both sides with screening members, connected to the cathode of the amplifying valve the grid of which is coupled to the scanning member provided with said screening members.

9. Apparatus for indicating irregularities in travelling textile material comprising means for conveying and guiding a textile material along a fixed path whereby an electrostatic charge is placed thereon, a scanning device supported alongside the path of moving textile material, said scanning device including an insulating member and at least two conductors coiled helically about said member whereby the electrostatic charge produced by any irregularity in the textile material may be induced therein, an electronic amplifier connected to each of said coiled con References Cited by the Examiner UNITED STATES PATENTS 2,010,683 8/35 Williams 206-65 2,295,795 9/42 Keeler 73-460 2,304,645 12/42 Keeler 73-160 2,326,928 8/ 43 Courson 206-65 2,929,245 3/ 60 Fischer 73160 RICHARD C. QUEISSER, Primary Examiner.

F. T. GARRETT, ROBERT L. EVANS. Examiners.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,187,568 June 8, 1965 Victor Emanuel Gonsalves et a1.

It is hereby certified that error appears in the above numbered patent reqiiring correction and that the said Letters Patent should read as correctedbelow.

Column 6, line 37, for "textile material" read traveling yarn Signed and sealed this 23rd day of November 1965.

(SEAL) Altest:

ERNEST W. SWIDER EDWARD J. BRENNER Almsting Officer Commissioner of Patents

Claims

9. APPARATUS FOR INDICATING IRREGULARITIES IN TRAVELLING TEXTILE MATERIAL COMPRISING MEANS FOR CONVEYING AND GUIDING A TEXTILE MATERIAL ALONG A FIXED WHEREBY AN ELECTROSTATIC CHARGE IS PLACED THEREON, A SCANNING DEVICE SUPPORTED ALONGSIDE THE PATH OF MOVING TEXTILE MATERIAL, SAID SCANNING DEVICE INCLUDING AN INSULATING MEMBER AND AT LEAST TWO CONDUCTORS COILED HELICALLY ABOUT SAID MEMBER WHEREBY THE ELECTROSTATIC CHARGE PRODUCED BY AN IRREGULARITY IN THE TEXTILE MATERIAL MAY BE INDUCED THEREIN, AN ELECTRONIC AMPLIFIER CONNECTED TO EACH OF SAID COILED CONDUCTORS TO RECEIVE THE ELECTROSTATIC CHARGE PRODUCED BY SUCH IRREGULARITY, MEANS FOR ELECTRONICALLY DIFFERENTIATING THE OUTPUTS OF SAID AMPLIFIERS TO PRODUCE A RESULTING SIGNAL AND ELECTRONIC MEANS RECEIVING AND RESULTING SIGNAL TO INDICATE THE PRESENCE OF SUCH IRREGULARITIES IN THE TEXTILE MATERIAL.