Yarn sensor for optically sensing a yarn moved in the longitudinal direction of the yarn

Abstract

In order to optically sense a yarn moved in the longitudinal direction of the yarn, a yarn sensor has a light source, a detector and a light guiding element. The yarn sensor is based on the effect of frustrated total internal reflection (FTIR). Because of the FTIR effect, scattered light exiting the light guiding element in the contact region between the yarn and an outer surface of the light guiding element is detected by means of the detector, in which case sensing of the yarn lying against the outer surface is enabled. Alternatively, the reduced intensity in the totally internally reflected beam is then sensed by the detector. The intensity in the totally internally reflected beam is reduced mainly by the scattered light coupled out of the light guiding element.

Claims

1. A yarn sensor for optically sensing a yarn moved in the longitudinal direction of the yarn, the yarn sensor comprising: a light source, a detector, and a light guiding element for guiding light emitted by the light source, wherein a yarn guiding element is present to bring the yarn into contact with an outer surface of the light guiding element, and wherein at least part of the light is coupled out of the light guiding element by contact with the yarn, and the detector senses light influenced by the yarn.

2. The yarn sensor according to claim 1, characterized in that the detector senses light coupled out of the light guiding element by the yarn.

3. The yarn sensor according to claim 1, characterized in that the detector senses remaining light that is guided by the light guiding element and is not coupled out by the yarn.

4. The yarn sensor according claim 1, characterized in that the light guiding element is comprised at least partly of a transparent ceramic.

5. The yarn sensor according to claim 1, characterized in that an outer surface of the light guiding element is convexly curved.

6. The yarn sensor according to claim 1, characterized in that the detector is a spatially resolving detector.

7. The yarn sensor according to claim 1, characterized in that the detector is an active pixel sensor.

8. The yarn sensor according to claim 1, characterized in that the light guiding element is part of a yarn guiding element.

9. A textile machine comprising a yarn sensor for optically sensing a yarn moved in the longitudinal direction of the yarn, wherein the yarn sensor comprises: a light source, a detector, and a light guiding element for guiding light emitted by the light source, wherein a yarn guiding element is present in order to bring the yarn into contact with an outer surface of the light guiding element, and wherein at least part of the light is coupled out of the light guiding element by contact with the yarn and the detector senses light influenced by the yarn.

10. The textile machine according to claim 9, characterized in that the detector senses light coupled out of the light guiding element by the yarn.

11. The textile machine according to claim 9, characterized in that the detector senses remaining light that is guided by the light guiding element and is not coupled out by the yarn.

12. The textile machine according claim 9, characterized in that the light guiding element is comprised at least partly of a transparent ceramic.

13. The textile machine according to claim 9, characterized in that an outer surface of the light guiding element is convexly curved.

14. The textile machine according to claim 9, characterized in that the detector is a spatially resolving detector.

15. The textile machine according to claim 9, characterized in that the detector is an active pixel sensor.

16. The textile machine according to claim 9, characterized in that the light guiding element is part of a yarn guiding element.

17. A method for optically sensing a yarn moved in the longitudinal direction of the yarn, by means of a light guiding element, comprising: guiding light by means of the light guiding element, bringing the yarn into contact with an outer surface of the light guiding element so that at least part of the light is coupled out of the light guiding element, and sensing the light influenced by the yarn.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further advantages and details of the yarn sensor according to the invention are explained on the basis of two preferred embodiment examples, without the subject matter of the invention being limited to these specific embodiment examples.

(2) The figures show:

(3) FIG. 1 is a schematic illustration of a workstation,

(4) FIG. 2 is a schematic illustration of a first embodiment example of a yarn sensor,

(5) FIG. 3 is a schematic illustration of a second embodiment example of a yarn sensor, and

(6) FIG. 4 is a snapshot of the yarn and a graph of an evaluation of a signal of a yarn sensor, which graph corresponds to the snapshot.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(7) FIG. 1 shows a schematic illustration of a workstation of a textile machine according to the invention. In the embodiment example, the textile machine is designed as an open-end spinning machine. A fiber band 2 is fed to a spinning box 1. The yarn 3 produced in the spinning box 2 is pulled out via a draw-off tube 4 by means of a draw-off roller pair 5. The yarn 3 runs through a yarn sensor 6 according to the invention and is wound, across a bow 8, by a back-and-forth movement of a thread guide 9 of a traversing device 7 over a specified width to form a cross-wound package 10.

(8) A friction roller 11 drives the cross-wound package 10. The thread guide 9 is arranged on a thread guide rod 12. The thread guide rod 12 is moved back and forth by a thread guide transmission 13. A drive unit 14 is provided in order to produce the back-and-forth movement of the thread guide transmission 13.

(9) From the illustration of FIG. 1, it is clear that, in order to monitor the running yarn 3, the yarn sensor 6 is arranged above the draw-off roller pair 5 in the traversing region of the yarn 3. This is not mandatory. It is also possible for the yarn sensor 6 to be arranged before the draw-off roller pair 5. The arrangement of the yarn sensor 6 is shown as an example here. The yarn sensor 6 can be provided at suitable points of the yarn run.

(10) The yarn sensor 6 is connected to a control device 16 by means of a signal line 15. The control device 16 is connected to the drive unit 14 by means of a further signal line 17. The drive unit 14 is preferably an electric motor. The control device 16 can be connected to further spinning positions, data processing devices and spinning machines (not shown) by means of a signal line 18.

(11) In FIG. 2, a first embodiment example of a yarn sensor 6 is shown. The yarn sensor 6 has a light source 19. The light source 19 is preferably an infrared LED. The light source 19 is arranged in a housing 20. In the embodiment example shown, the housing 20 also serves as a retainer for a light guiding element 21. The light guiding element 21 is designed as a round bar. The material of the light guiding element 21 is preferably a transparent ceramic.

(12) Only to illustrate the principle of the invention, reference number 22 is used to indicate beams that the light source 19 emits. The beams 22 are reflected at the outer surface 23. The light source 19 and the light guiding element 21 are designed in such a way that total internal reflection is achieved when no yarn is in contact with the outer surface 23 of the light guiding element 21.

(13) In the embodiment example shown in FIG. 2, a yarn 3 is shown schematically. The yarn 3 lies against the outer surface 23 of the light guiding element 21. A contact area 24 lies between the yarn 3 and the outer surface 23. The contact of the yarn 3 with the light guiding element 21 results in frustrated total internal reflection in the region of the contact area 24, because the index of refraction of the yarn 3 is greater than the index of refraction of the air surrounding the yarn sensor 6. Because of the frustrated total internal reflection, the light that exits the light guiding element 21 in the region of the contact area 24 is scattered at the yarn. The scattered light propagates through the light guiding element 21, as indicated by the beam 25. Said scattered light is detected by means of a detector 26. The detector 26 provides signals, which can be fed to the control device 16, for example.

(14) FIG. 3 shows a second embodiment example of a yarn sensor. The yarn sensor 6 comprises a light source 19, which is arranged in a housing 20. The housing 20 also serves as a retainer for a light guiding element 21. Likewise in this embodiment example, the yarn 3 lies against an outer surface 23 of the light guiding element 21. The difference between the embodiment according to FIG. 3 and the embodiment according to FIG. 2 lies in the arrangement of the detector 26 and in the evaluation methodology associated therewith. Instead of the scattered light, which should be indicated by the beam 25 and which is coupled out of the light guiding element 21, the reduced intensity in the totally internally reflected beam 27 is evaluated.

(15) The detector 26 is preferably a pixel sensor, more particularly an active pixel sensor. In FIG. 4, a snapshot of the scattered light that a detector has sensed is shown. The evaluation of said snapshot is shown in a graph. It is clear that a yarn lies against the light guiding element.

(16) The yarn diameter can be inferred from the width B of the detector signal, because, at constant thread tension, the scattered light is proportional to the yarn diameter. Thus, thin and thick places in the yarn can also be detected.

(17) From the change in the detector signal over time, it can also be stated whether the tension of the yarn has changed.

LIST OF REFERENCE NUMBERS

(18) 1 Spinning box 2 Fiber band 3 Yarn 4 Draw-off tube 5 Draw-off roller pair 6 Yarn sensor 7 Traversing device 8 Bow 9 Thread guide 10 Cross-wound package 11 Friction roller 12 Thread guide rod 13 Thread guide transmission 14 Drive unit 15 Signal line 16 Control device 17 Signal line 18 Signal line 19 Light source 20 Housing 21 Light guiding element 22 Beams 23 Outer surface 24 Contact area 25 Beam 26 Detector 27 Beam

(19) It will therefore be readily understood by those persons skilled in the art that the present invention is susceptible of broad utility and application. Many embodiments and adaptations of the present invention other than those herein described, as well as many variations, modifications and equivalent arrangements, will be apparent from or reasonably suggested by the present invention and the foregoing description thereof, without departing from the substance or scope of the present invention. Accordingly, while the present invention has been described herein in detail in relation to its preferred embodiment, it is to be understood that this disclosure is only illustrative and exemplary of the present invention and is made merely for purposes of providing a full and enabling disclosure of the invention. The foregoing disclosure is not intended or to be construed to limit the present invention or otherwise to exclude any such other embodiments, adaptations, variations, modifications and equivalent arrangements.