Title of Invention

A METHOD AND A DEVICE FOR CONTACTLESS DETERMINATION OF REAL-TIME INSTANTANEOUS SPEED OF A RUNNING THREAD AT A WINDING MACHINE

Abstract

For contact-free determination of the speed of a running thread with a sensor unit on a winding head of a textile machine, a laser beam (35) is generated from a light source. This laser beam is divided into two laser beams (35, 36) which again meet on the running thread (2). From the light reflected by the thread, measuring signals are generated with the help of the Laser-Doppler-Anemometry-method. The measured signals are evaluated for length measurement and taken into account for exact determination of yarn defects. The invention can be applied in a cost-effective manner and serves the purpose of the quality improvement of the thread (2).

Full Text

Description Method and Device for Contact-free Determination of the Speed of a Running Thread The invention pertains to a method for a contact-free determination of the speed of a running thread according to the introductory part of claim 1 and a device according to the introductory part of claim 6. Winding heads of modern textile machines for production of cross-wound bobbins are equipped with units for speed measurement and length measurement of the running thread. Constantly increasing specifications for the quality of yarn have led to monitoring of yarn parameters, e.g. the yarn diameter, not only at selected winding heads but also at each individual winding head. While monitoring the yarn diameter, in order to evaluate whether a deviation from the rated yarn diameter should be categorised as yarn defect, generally also the length and the deviation is taken into account. Therefore, determination of the exact defective length is a significant component of quality control of yarn. Classical, mechanical measuring methods for speed measurement of the running thread work with unwinding measuring wheels. With the occurrence of slippage, friction sets in between the yarn and the surface of the measuring wheel Apart from the measuring errors occurring due to the slippage, in case of sensitive threads disadvantageous quality handicaps can also occur due to friction. In order to avoid such disadvantages, use of contact-free measuring methods are known in the textile industry. For experimental contact-free speed measurement of single fibres in the air current of the fibre guiding channel, as used in an open-ended spinning machine, it is known from Bauer's "Laser-Doppler-Anemometry", chemical fibres/textile industry 37789. (1987) September pages 829 and 832, that one uses the method of Laser-Doppler-Anemometry (referred to below as LDA). The described LDA-method is suggested merely for research purposes in the field of experimental flow mechanics or flow-technical investigations of fibre air currents, the way they are carried out primarily in research of new spinning methods. Till now, without applying LDA-method, flow-technical optimisation measures were only possible in a restricted manner. Ringen's literature a.o. "Opto-electronic sensor for contact-free speed measurement on textile surfaces", textil praxis international (1988), June, pages 640 to 643, describes the speed measurement on surfaces of goods assembly lines, e.g. fabrics, which are carried out within the scope of a research project. The described reference beam-Doppler-anemometry-method is based on the Doppler effect. When transmitters and receivers move relatively towards one another, there occurs a frequency shift as a function of the relative velocity. By evaluating the frequency shift, the speed of the moved body can be determined, if the receiver is location-fixed. In the reference beam-Doppler -anemometry-method, one works with a reference beam and a measuring beam. Thereby the reference wave not shifted in the frequency and the reflected dispersed light of the Doppler-shifted measuring beam get superimposed in the receiver. The reference beam method has the disadvantage, that the intensity of the reference beam and the intensity of the measuring beam reflected from the surface clearly differ from one another. In order to obtain the same intensity as the measuring beam, which is a prerequisite for a good so-called "signal to noise ratio", the reference beam must be significantly weakened. But this is possible only in a restricted manner, as the dispersion capacity of moving particles depends on their size and surface. Moreover, if one uses such commercial measuring systems, then one requires a lot of structural and evaluation-technical effort In the literature of Backmann a.o. "Contact-free speed measurement on the running thread", Melliand Textilberichte (1993) 7, pages 639 to 640, it is mentioned that although the document describes the speed measuring methods according to the principle of LDA, for actual practice there is no cost-effective LDA-measuring method existing so far. The total complication for such measuring systems, in spite of miniaturisation and adaptation of optical components, is still considered as extremely high. Therefore, in this publication, as a suitable alternative possibility for practical application, the co-relation measuring method is investigated and described. The LDA-methods handled in available literature do pertain to applications as experiments in laboratories for research purpose, whereby significant complexity and high costs are taken into one's stride. An application in textile machines, which have a large number of work stations, does not seem meaningful on account of high costs and less structural space available and is even mentioned in the literature as impossible. The generic document DE 42 25 842 A1 describes a device for measuring the speed of textile threads on a bobbin carriage according to the co-relation measuring method. While winding or rewinding spinning cops on to a cross-wound bobbin, a to and fro movement is transmitted to the thread, transverse to the thread running direction. On account of this to and fro movement, the speed of the thread passing through a sensor varies by approx. ±35%, depending on the shifting frequency of the thread. If for example, the momentary thread speed is determined as the average value from the measured values, then the evaluation of the yarn defective length for cleaning up of the yarn is correspondingly erroneous. Thus there is the danger of decrease in quality of the yarn and productivity losses of the textile machine. The thread speed in winding machines for rewinding the thread is approx. ten times greater than the spinning machine, in which the spun thread is wound on to a bobbin at the spinning head. In case of such high thread speeds and shifting frequencies gap-free preparation of the signals could lead to difficulties. It could be the case that the computing capacity of the used commercial micro-processors are by far not sufficient for the purpose. It is the task of this invention to improve the determination of the speed of the running thread at one work station of a multiple station textile machine. This task is fulfilled with the help of a method having the features as mentioned in claim 1 and with the help of a device having the features as mentioned in claim 6. Advantageous extensions of the invention form the subject of the sub-claims. From a light source a laser beam is generated, which is divided into two beams which again come together on the running thread. The intensity of the beams, both of which work together as measuring beams, are equated. Thus one gets a good signal to noise ratio. The generation of measuring signals from both the laser beams reflected according to the LDA-method allow a highly precise speed determination or length determination, for which the computing volume involved can be easily handled by commercially available micro-processors. On the basis of this highly precise measurement, in conjunction with a measurement of the thread diameter, the lengths of defective yarn can also be determined in an extraordinarily precise manner. Thus the categorisation of tolerable yarn defect on the one hand, and the yarn defect to be cleaned up by cutting the thread on the other hand, can take place in a more appropriate manner. Not tolerable defects are identified completely and correctly. The cleaning up of tolerable yarn defects, which on account of shortcomings in the speed determination according to the state-of-the-art technology are erroneously categorised as not tolerable, as well as creation of unnecessary thread joining points are avoided. This enhances the yarn quality and the productivity of the winding head. If according to claim 3 or claim 7, the laser beam additionally serves the purpose of determination of the diameter of the thread, and if according to claim 5 or claim 9 the light of the laser beam reflected by the thread is additionally evaluated for an alien fibre identification, then the number of structural components can be significantly reduced. Then it is no longer necessary to have an own light source for determining the diameter. The space requirement for the sensor unit will be smaller. A further reduction in complication can be achieved, if according to claim 4 only elements for determining the magnitude of the speed are used. Therefore, for example, one can dispense with the generally used Bragg-cell for determination of the movement direction in case of the LDA-method. Thus the required complexity of devices also gets reduced. The invention allows a dynamic measurement of the yarn speed, i.e. a measurement in which for evaluation of yarn defects, constantly the momentary yarn speed is determined and not say an average value of the yarn speed. Also the computation job with usual processors, as used at a work station of a winding machine or a spinning machine, can be handled without any problem. It is possible to determine the yarn speed with very high time resolution and hence in a very precise manner. With advantageous extensions of this invention, particularly also the complexity of construction and cost-intensity can be significantly reduced. With the knowledge of the above mentioned publications, the world of experts did not find this state-of-the-art technology as exciting for over a decade and did not hit upon the idea for using the LDA- method online at the work stations of a multiple station textile machine, as one finds in the case of winding machines or spinning machines with several winding heads. Moreover, as one can also see from the publication, the experts' world was of the opinion that in spite of miniaturisation and adaptation of optical components for such measuring systems, it would still be rather complicated and cumbersome and hence the LDA-method should only be used for laboratory set-ups for research purposes. The world of experts has till today not recognised the fact that the LDA-method can be carried out in such a version, that the costs and the space requirement at the winding head can be kept within an acceptable framework. The advantage of a highly precise contact-free measurement can speak for this invention, without having to take into the consideration the disadvantages hitherto associated with it, like high costs or insufficient computing capacity. The highly precise determination of the yarn speed is taken up during the production of each individual bobbin. This extreme advantage was not utilised so far. With the help of the invention the yarn cleaning in winding machines or spinning machines is significantly improved. Unnecessary cleaner cuts warranted on account of defective yarn speed during evaluation of the speed of yarn defects can be avoided. Yarn defects to be eliminated, which cannot be determined with the help of known devices and methods, can be identified by means of the object of the invention. Thus the productivity of the machine as well as the quality of the yarn will get enhanced. Further details about the invention are explained below in details on the basis of the design example shown in the figures. The following are shown: Fig. 1 A simplified representation of a winding head of a winding machine with a measuring head, which is equipped for speed measurement; Fig. 2 A principle sketch of the design and structure of the speed measuring device; Fig. 3 A simplified representation of interference bands; Fig. 4 An LDA-signal; Fig. 5 A principle sketch of aspeed measuring device with reverse dispersal; Fig. 6 A principle sketch of an alternative design of a speed measuring device. Fig. 1 shows a winding head 1 of a spooling machine, in which the thread run of the thread 2 is shown between a spinning cop 3 as feeding bobbin and a cross-wound bobbin 4 as winding bobbin. The thread 2 drawn off from the spinning cop 3 during the winding sequence passes through a thread tension unit 5, a cutting unit 7 and a measuring head 6. The thread 2 gets wound in the bobbin carriage 8 on to the cross-wound bobbin 4 which is shown in fig. 1 as rotating in clockwise direction. During the winding process, the cross-wound bobbin 4 lies with its surface on a supporting roller 9 designed as tension roller and takes along this drive- less tension roller due to friction locking. The drive of the cross-wound bobbin 4 takes place over the axis of the cross-wound bobbin 4 with the help of the drive unit arranged directly against spool frame 10 or integrated within the spool frame 10. For traversing the thread 2 during the winding process, the winding head 1 has a thread traversing unit 27. The displacement of the thread 2 takes place with the help of a thread guide 28 which is moved to and fro in the direction of the rotation axis of the cross-wound bobbin 4. A computer 11 comprises of a control unit, an evaluating unit for the measured values of the measuring head 6, as well as a storage/memory unit. The computer 11 is connected through the line 12 to additional computers, control units and data storage units which are not shown in details here on account of simplicity. The principle structure of a measuring head 6 as per the invention is shown in fig. 2. The laser 13 which is used as light source generates a laser beam 14 whose frequency is known very precisely. On the plate 15 the laser beam 14 gets divided into two laser beams 16, 17. Both the laser beams 16, 17 have the same intensity. The laser beam 17 is deflected by the mirror 18 in such a way that it runs up to the lens 19, parallel to the laser beam 16. With the help of the lens 19 the laser beams 16, 17 are aligned in such a way that both meet at the focal point of the lens 19. The focal point lies in the zone of the thread 2. Both laser beams 16, 17 work as measuring beams. The laser light of the laser beam 16, 17 is dispersed by the surface of the thread 2 on which they meet. When the thread 2 moves, a relative movement takes place between the laser 13 as transmitter of the light waves and the thread 2 as the receiver. In this case, there occurs a change in the light waves reflected by the thread as a function of the relative velocity, which is known as the Doppler effect. The light waves of the laser beams 16, 17 reflected by the thread 2 form the interference band 21 from the dark and bright zones, an interference pattern 20 in the room, as shown for example in fig. 3, whereby the light waves of both laser beams 16, 17 get superimposed. If a suitable receiver is placed in this room, then the interference pattern 20 becomes visible. The zone which both the laser beams 16, 17 penetrate is designated as measured volume. As receiver one uses a detector 22, which has two apertures 23, 24, a collective lens 25 and a sensor element 26. The dispersed light reflected from the thread is shielded from the sensor element 26 by the aperture 23. The collective lens 25 focuses only dispersed light reflected from the thread 2 as so-called reverse dispersal on to the sensor element 26. The sensor element 26 takes up an intensity oscillating with the beat frequency Fs. The beat frequency Fs is obtained from the difference of both the Doppler-displaced light frequencies FD1 and FD2 of the laser beams 16, 17. The method with the division of the laser beam 14 generated by the laser 13, as described above, into the laser beams 16 and 17, is referred to as LDA-double beam-method. In the LDA-double beam-method the detected beat frequency Fs is not dependent on the position of the detector 22 in relation to the thread. Therefore, the detector 22 can be placed in a by and large freely selectable position, and the collective lens 25 focusing the dispersed light can be designed with a large diameter. The graph 51 of a detected speed signal, of a part traversing the measured volume, over the time t, is shown in fig. 4. The sensor element 26 takes up an intensity I of the light which is largely determined by the intensity distribution in the laser beam 14 and by the beat frequency Fs of both the Doppler-displaced light waves. The graph of the light intensity detected by the sensor element 26 is processed through corresponding evaluation algorithms and the signals relevant for the speed of the thread are separated, evaluated and converted into a digitalized speed signal. As shown in fig. 2, the measuring head 6 comprises of, besides the elements for determining the speed, also elements for determining the diameter of the thread 2. The light emitted by a light source 29 passes through an optical element 30 and is reflected by the thread 2. Reflected light is detected by a sensor 31. The measured signals generated as a function of light intensity are evaluated in the computer 11 for determining the diameter of the thread 2. Fig. 5 shows an alternative structure of the measuring head 6. The laser 32 generates a laser beam 33 which is divided by the plate 34 into two laser beams 35, 36 with equal intensity. The mirror 37 deflects the laser beam 36 in such a way, that it runs parallel to the laser beam 35. Both the laser beams 35, 36 are focused on to the thread 2 by the optical module 38. The dispersed light reflected by the thread 2 is diverted by the optical modules 38 and 39 on to the sensor 40. The measuring head which works with reverse dispersal can have a compact, space-saving structure. Determination of the diameter of the thread 2 takes place with the help of a measuring unit 41, which has a light source 42, an optical module 43 and a sensor 44. The sensor 44 is arranged in such a way that the shadows cast on it by the thread 2 get imaged. The sensor 44 can be designed as a simple photo cell or as CCD-line sensor. Fig. 6 shows another alternative design of the measuring head 6 in a simplified representation. The design for speed determination corresponds to the design shown in fig. 1. For determining the diameter of the thread 2, the plate 45 forms a partial beam 46 of the laser beam 14 generated by the laser 13; this is then deflected by the mirror 52 and directed on to the thread 2 with the help of the optical module 47. The sensor 48 detects the light which is dependent on the diameter of the thread 2 and delivers measured signals to the computer 11, from which the diameter of the thread 2 is determined. An evaluation of the measured signals of the sensors 48 and 50 can take place as a component of an alien fibre identification. Alternatively, the evaluating unit which serves the purpose of evaluation of the speed measuring signals, the thread diameter measuring signals of the alien fibre identification signals or of all types of measured signals together, can also be a module of the measuring head 6. The thread 2 is continuously subjected to quality monitoring. For this, apart from the speed, the diameter or the thickness of the running thread 2 is also determined with the help of the measuring head 4 which works contact-free. The measured signals are evaluated and the thread speed is calculated. With the help of the integrator, which is part of the evaluating unit, the thread speed is evaluated for cumulative length determination of the thread 2. If the measuring head 6 gives an undue over estimation or under estimation of the thickness of the thread 2, then the length of this yarn defect is determined with the help of the computer 11. If one sees that there is a yarn defect, which is not permissible according to pre-given cleaning limits of a quality matrix, then the cutting unit 7 is activated and a cleaner cut is carried out in a already known method. After eliminating the defective thread section by cutting off, as known for example from the document DE 196 14 184 A1 or a parallel US patent no. 5, 852, 660, the thread ends are joined again in a splicing unit 49 and the winding sequence is subsequently continued. In conjunction with highly precise measurement, one can also achieve a qualitatively high quality monitoring of the thread 2. The high measuring safety allows a reduction in the cleaner cuts and hence in the yarn quality, as well as an increase in productivity by avoiding unnecessary interruption of the winding sequence. The invention is not restricted to the design examples shown. Within the scope of the thought behind the invention, further alternative extensions are possible, without actually deviating from the general spirit of the invention. WE CLAIM 1. Method for contact-less determination of the speed of a running thread at a winding head of a textile machine with the help of a sensor unit, in which a laser beam (14, 33) is generated from a light source and this laser beam is divided into two laser beams (16, 17; 35, 36); the two laser beams (16, 17; 35, 36) are guided in such a way that they again meet on the running thread (2); measuring signals are generated from the light reflected by the thread (2); the generation of the measuring signals takes place according to the Laser-Doppler-Anemometry-method; the measured signals are evaluated for length measurement and the result of the length measurement is taken into account for precise determination of yarn defects. 2. Method as per claim 1, in which for determining yarn defects, the thread diameter is detected and quality improvement of the thread (2) is undertaken with the help of a yarn cleaner. 3. Method as per claim 1 or 2, in which a laser beam (14) generated for speed measurement according to the Laser-Doppler- Anemometry-method also additionally serves the purpose of the measurement of the diameter of the thread (2). 4. Method as per one of the claims 1 to 3, in which only elements for determining the magnitude of the speed are used without ascertaining the movement direction. 5. Method as per one of the claims 1 to 4, in which the laser beams (16, 17; 35, 36) reflected by the thread (2) are additionally evaluated for an alien fibre identification. 6. Device for contact-free determination of the speed of the thread (2) with a sensor unit, in which the device is arranged on a winding head of a textile machine; the sensor unit comprises of a light source for generating a laser beam (14, 33) and an optical unit which is designed in such a way that the laser beam (14, 33) is divided into two laser beams (16, 17; 35, 36) which again meet on the running thread (2); the device has a detection unit (22) with a receiver and an imaging optical mechanism arranged in front of the receiver, as well as an evaluating unit which is programmed in such a way that it processes the measured signals for determining the speed of the thread (2). 7. Device as per claim 6, in which the evaluating unit comprises of an integrator with which a thread length can be determined from the speed of the thread (2), and the sensor unit has elements for detecting the diameter of the thread (2). 8. Device as per one of the claims 6 or 7, in which the sensor unit is programmed for alien fibre identification. 9. Device as per one of the claims 6 to 8, in which the components for alien fibre identification are arranged along with the components for speed measurement in a common housing. For contact-free determination of the speed of a running thread with a sensor unit on a winding head of a textile machine, a laser beam (35) is generated from a light source. This laser beam is divided into two laser beams (35, 36) which again meet on the running thread (2). From the light reflected by the thread, measuring signals are generated with the help of the Laser-Doppler-Anemometry-method. The measured signals are evaluated for length measurement and taken into account for exact determination of yarn defects. The invention can be applied in a cost-effective manner and serves the purpose of the quality improvement of the thread (2).

Documents:

555-KOL-2004-(27-01-2012)-CORRESPONDENCE.pdf

555-KOL-2004-ABSTRACT 1.1.pdf

555-KOL-2004-ABSTRACT-1.2.pdf

555-kol-2004-abstract.pdf

555-KOL-2004-AMANDED CLAIMS-1.1.pdf

555-KOL-2004-CLAIMS.pdf

555-KOL-2004-CORRESPONDENCE 1.2.pdf

555-KOL-2004-CORRESPONDENCE-1.1.pdf

555-KOL-2004-CORRESPONDENCE-1.3.pdf

555-kol-2004-correspondence.pdf

555-KOL-2004-DESCRIPTION (COMPLETE) 1.2.pdf

555-KOL-2004-DESCRIPTION (COMPLETE)-1.3.pdf

555-kol-2004-description (complete).pdf

555-KOL-2004-DRAWINGS 1.1.pdf

555-KOL-2004-DRAWINGS-1.2.pdf

555-kol-2004-drawings.pdf

555-KOL-2004-ENGLISH TRANSLATED OF PRIORITY DOCUMENT.pdf

555-KOL-2004-FORM 1 1.1.pdf

555-KOL-2004-FORM 1-1.2.pdf

555-kol-2004-form 1.pdf

555-kol-2004-form 18.pdf

555-KOL-2004-FORM 2 1.1.pdf

555-KOL-2004-FORM 2-1.2.pdf

555-kol-2004-form 2.pdf

555-KOL-2004-FORM 3 1.1.pdf

555-kol-2004-form 3.pdf

555-kol-2004-form 5.pdf

555-KOL-2004-OTHERS.pdf

555-KOL-2004-PA.pdf

555-KOL-2004-PETITION UNDER RULE 137.pdf

555-kol-2004-priority document.pdf

555-KOL-2004-REPLY TO EXAMINATION REPORT.pdf

555-kol-2004-specification.pdf