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1. WO2020115649 - PROCÉDÉ ET CAPTEUR DE MESURE DE ROTATION D'UN D'OBJET ALLONGÉ

Note: Texte fondé sur des processus automatiques de reconnaissance optique de caractères. Seule la version PDF a une valeur juridique

[ EN ]

CONCLUSIONS

1. Method for contactless measurement of local rotation of an elongated, substantially non-conducting or poorly conductive object, preferably a yarn, the method comprising the following steps:

a. guiding the object along a longitudinal axis through at least one detection arrangement comprising a plurality of electric charge detecting components, characterised in that said electric charge detecting components are arranged in a first substantially circular pattern around the longitudinal axis at equal mutual distances, and comprising a plurality of grounding electrodes equal to the plurality on electric charge detecting components, which grounding electrodes are arranged in a second substantially circular pattern around the longitudinal axis at equal mutual distances, the second substantially circular pattern staggered with respect to the first substantially circular pattern, the grounding electrodes functioning as a screen between the successive charge detecting components and thereby acting as a spatial filter;

b. detecting one or more electrical charges on the object by a plurality of the charge detecting components, and processing the detection into an output signal;

c. combining the output signals of each of the charge detecting components; d. deriving one or more, preferably one, dominant frequencies from the combined output signals.

2. Method according to the preceding claim 1, wherein the dominant frequencies are derived by applying a Discrete Fourier Transform (DFT), preferably Fast Fourier Transform (FFT) or Discrete-Time Fourier Transform (DTFT), to the merged output signals over a certain period of time.

3. Method according to the preceding claim 1, wherein the dominant frequencies are derived from the merged output signals by measuring the number of peaks in the merged output signals over a given period of time.

4. Method according to any of the preceding claims 1 to 3, the electric charge detecting components comprising two separate groups, the electric charge detecting components of the two groups being arranged in alternating succession in the first circular pattern at equal distances from each other, and the dominant frequencies being determined on the basis of the difference of the output signals of the first group and the second group, preferably wherein the electric charge detecting components of the first group are connected in series, and wherein the electric charge detecting components of the second group are connected in series.

5. A method according to any of the preceding claims 1 to 4, wherein the local rotation is derived on the basis of the dominant frequencies and the distance between successive charge detecting components and/or grounding electrodes.

6. Method according to any of the preceding claims 1 to 5, wherein the merged output signals are subjected to a small band filter, which small band filter is centred around the dominant frequency, and wherein local rotation of the elongated object is quantified on the basis of the filtered output signals.

7. Device for contactless measurement of local rotation of an elongated object extending substantially along one dimension, preferably a yarn, comprising one or more detection arrangements, the detection arrangements each comprising a plurality of electric charge detecting components, characterised in that said electric charge detecting components are arranged in a first substantially circular pattern about a longitudinal axis and comprise a plurality of grounding electrodes equal to the plurality of electric charge detecting components, which grounding electrodes are arranged in a second substantially circular pattern around the longitudinal axis, the second substantially circular pattern staggered with respect to the first substantially circular pattern, wherein the grounding electrodes act as a screen between the successive charge detecting components and thus act as a spatial filter, said device further comprising a processor coupled to the one or more detection arrangements, and said processor being adapted to determine deriving one or more, preferably one, dominant frequencies from output signals of the detection arrangements.

8. Device for contactless measurement of local rotation according to the preceding claim 7, wherein the first and second circular pattern have a substantially equal radius, and together form essentially a single circular pattern.

9. Device for contactless measurement of local rotation according to any of the preceding claims 7 to 8, the electric charge detecting components comprising two separate groups, the electric charge detecting components of the two groups being arranged in alternating succession in the first circular pattern at equal distances from each other, and the dominant frequencies being determined on the basis of the difference of the output signals of the first group and the second group, preferably wherein the electric charge detecting components of the first group are connected in series, and wherein the electric charge detecting components of the second group are connected in series.

10. Device for contactless measurement of local rotation according to any of the preceding claims 7 to 9, wherein the electric charge detecting components comprise antennas, which extend essentially parallel to each other perpendicular to the first circular pattern over a predetermined distance.

11. Device for contactless measurement of local rotation according to the preceding claim 10, wherein the antennas extend over a predetermined length along the longitudinal axis, which predetermined length is at least 3 mm, preferably at least 5 mm, and at most 100 mm, preferably at most 50 mm.

12. Device for contactless measurement of local rotation according to any of the preceding claims 7 to 11, comprising a digital signal processor (DSP) for processing output signals of the electric charge detecting components, preferably comprising a low-pass filter.

13. Device for contactless measurement of local rotation according to any of the preceding claims 7 to 12, wherein the circular pattern has a minimum radius of 0.5 mm, preferably at least 1 mm, more preferably at least 2 mm.

14. Device for contactless measurement of local rotation according to any of the preceding claims 7 to 13, wherein the circular pattern has a shortest distance with respect to the surface of the elongated object of at least 0.01 mm, preferably at least 0.1 mm, more preferably at least 0.5 mm, and still more preferably at least 1 mm.

15. Device for contactless measurement of local rotation according to any of the preceding claims 7 to 14, wherein the circular pattern has a maximum radius with respect to the surface of the elongated object of at most 100 mm, preferably at most 75 mm, more preferably at most 50 mm, and still more preferably at most 25 mm.

16. Device for contactless measurement of local rotation according to any of the preceding claims 7 to 15, wherein the circular pattern has a shortest distance to the surface of the elongated object of at most 100 mm, preferably at most 75 mm, more preferably at most 50 mm, and still more preferably at most 25 mm.

17. Method for contactless determination of undergone rotation of a yarn extending substantially along a longitudinal axis at a predetermined longitudinal point on a yarn over a certain path along the longitudinal axis or duration of time during the twisting of said yarn in an air jet device, comprising the following steps: a. measuring local rotation, preferably according to a method according to any of the preceding claims 1 to 6, at at least one, preferably at least 2, 3, 4, 5 or more, immobile, separated positions along the longitudinal axis of the yarn, said positions being upstream along the yarn relative to, and/or at the level of the location where the yarn is provided with torsion by an external actuator, preferably wherein at least one of the positions is at a distance of at most 10 cm from where the yarn is provided with torsion by an external actuator, preferably wherein at least one of the positions is in the air jet device itself;

b. calculating, on the basis of the measured rotation, the total undergone rotation of the yarn at the predetermined longitudinal point of the yarn over said path.

18. Method for contactless determination of undergone rotation according to the preceding claim 17, wherein the calculation of the rotation undergone is done on the basis of an interpolation, and optionally an extrapolation, of the measured local rotation, the total rotation of the said predetermined longitudinal point on the yarn being calculated on the basis of an integration or weighted summation of the measured and/or interpolated, and optionally extrapolated, rotation at longitudinal positions of said predetermined longitudinal point of the yarn at the times when said predetermined longitudinal point of the yarn is at said longitudinal positions, starting from a substantially known, or approximately derivable, longitudinal velocity profile of the yarn.

19. Method for contactless determination of undergone rotation according to any of the preceding claims 17 or 18, wherein the measuring of the local rotation comprises the following steps:

a. guiding the yarn along the longitudinal axis through at least one, preferably 2, 3, 4, 5 or more, detection arrangements at said positions along the longitudinal axis, each detection arrangement comprising a plurality of electric charge detecting components that are arranged in a first substantially circular pattern around the longitudinal axis at equal mutual distances, and comprising a plurality of grounding electrodes equal to the plurality of electric charge detecting components, which

grounding electrodes are arranged in a second substantially circular pattern around the longitudinal axis at equal mutual distances, the second substantially circular pattern staggered with respect to the first substantially circular pattern, wherein the grounding electrodes act as a screen between the successive charge detecting components and thus act as a spatial filter;

b. detecting one or more electrical charges on the yarn by a plurality of the charge detecting components, and processing the detection into an output signal;

c. combining the output signals of each of the charge detecting components according to an identical schedule;

d. deriving one or more, preferably one, dominant frequencies from the combined output signals.

20. Method for contactless determination of undergone rotation according to any of the preceding claims 17 to 19, wherein the undergone rotation is determined at two separate longitudinal points on the yarn, and wherein a torsion of the yarn between said two separate longitudinal points is determined by subtracting the rotations undergone from the two separate longitudinal points.

21. Method for applying a torsion to a yarn via a substantially tangential air current at a fixed location relative to the, preferably longitudinally moving, yarn, wherein the air current is controlled on the basis of torsion of a section of the yarn with a predetermined length, which section is located at said fixed location, and wherein the torsion is determined by a method according to the preceding claim 18.

22. System for manufacturing a twisted yarn from a, preferably substantially torsion- free, yarn that is presented along a longitudinal axis, the system comprising the following elements:

a. an air jet device for applying a torsion to the yarn, to obtain a twisted yarn;

b. at least 1, preferably at least 2, more preferably at least 5, devices for contactless measurement of local rotation of the yarn according to any of the preceding claims 7 to 16, wherein the devices are positioned along the longitudinal axis separately from each other upstream in front of the yarn relative to and/or at the level of the air jet device, preferably wherein at least one of the devices is positioned at a maximum upstream distance

of 10 cm with respect to the air jet device, and is preferably integrated in the air jet device.