METHOD AND APPARATUS FOR DETERMINING THE FIBER ORIENTATION

Abstract

An apparatus and an associated method determine the fiber orientation of a moving fibrous web, in particular a paper, cardboard or cellulose web. An illumination device illuminates an area of the fibrous web and a camera records a digital image of the illuminated area of the fibrous web. The illumination device is configured to illuminate the fibrous web for a period of time of 1 μs or less and the camera is configured in such a way that the edge length of a pixel corresponds to no more than 20 μm, in particular no more than 10 μm.

Claims

1-16. (canceled)

17. A method for determining the fiber orientation of a moving fibrous material web, paper web, cardboard web or cellulose web, the method comprising: illuminating an area A of the fibrous material web for a time period Δt; recording a digital image of the illuminated area A; setting the time period Δt to be at most 1 μs; and providing the digital image with a sufficiently high resolution to cause an edge length of a pixel to correspond to less than 20 μm of the imaged area A.

18. The method according to claim 17, which further comprises: setting the time period Δt to be at most 500 ns; and providing the digital image with a sufficiently high resolution to cause the edge length of the pixel to correspond to less than 10 μm of the imaged area A.

19. The method according to claim 17, which further comprises calculating a fiber orientation from data of the digital image.

20. The method according to claim 17, which further comprises carrying out an illumination of the area A by light having wavelengths in a range of 450 nm-780 nm.

21. The method according to claim 20, which further comprises carrying out the illumination of the area A by light having wavelengths in a range of between 450 nm and 550 nm.

22. The method according to claim 20, which further comprises carrying out the illumination of the area A by light having wavelengths in a range of 600 nm-700 nm.

23. The method according to claim 17, which further comprises using wavelengths for an illumination of the area A having a bandwidth of at most 100 nm.

24. The method according to claim 17, which further comprises using wavelengths for an illumination of the area A having a bandwidth of at most 50 nm.

25. The method according to claim 17, which further comprises directing light of an illumination of the area A to be incident on the fibrous material web at an angle α deviating at most 45° from the perpendicular.

26. The method according to claim 17, which further comprises directing light of an illumination of the area A to be incident on the fibrous material web at an angle α deviating between 25° and 40° from the perpendicular.

27. The method according to claim 17, which further comprises providing the illuminated area A as a square of at least 5 mm×5 mm.

28. The method according to claim 17, which further comprises providing the illuminated area A as a square of 10 mm×10 mm.

29. The method according to claim 17, which further comprises moving the fibrous material web at a speed of greater than 1000 m/min.

30. The method according to claim 17, which further comprises moving the fibrous material web at a speed of greater than 1200 m/min.

31. An apparatus for determining the fiber orientation of a moving fibrous material web, paper web, cardboard web or cellulose web, the apparatus comprising: an illumination device for illuminating an area A of the fibrous material web, said illumination device configured to illuminate the fibrous material web for a time period of 1 μs or less; and a camera for recording a digital image of the illuminated area A of the fibrous material web, said camera configured to cause an edge length of a pixel to correspond to at most 20 μm.

32. The apparatus according to claim 31, wherein said camera is configured to cause the edge length of the pixel to correspond to at most 10 μm of the illuminated area A.

33. The apparatus according to claim 31, which further comprises a processing unit configured to calculate a fiber orientation from data of the digital image of the camera.

34. The apparatus according to claim 31, wherein said illumination device includes a plurality of light sources or LEDs disposed uniformly and annularly around said camera.

35. The apparatus according to claim 34, wherein said plurality of light sources or LEDs is an odd number of light sources or LEDs.

36. The apparatus according to claim 31, wherein said illumination device is configured to direct light being incident on the fibrous material web at an angle α deviating at most 45° from the perpendicular.

37. The apparatus according to claim 31, wherein said illumination device is configured to direct light being incident on the fibrous material web at an angle α deviating between 25° and 40° from the perpendicular.

38. The apparatus according to claim 31, which further comprises a plate being entirely or substantially transparent to light of the illumination device, said plate being disposed at least one of between said illumination device and the fibrous material web or between said camera and the fibrous material web.

39. The apparatus according to claim 31, wherein said illumination device is at least temporarily capable of being operated at an amperage of at least 10 A.

40. The apparatus according to claim 31, wherein said camera has optical properties and a lens with aperture settings using apertures between F4 and F16, enabling a resolution corresponding to the edge length of the pixel of at most 20 μm of the illuminated area A.

41. The apparatus according to claim 32, wherein said camera has optical properties and a lens with aperture settings using apertures between F4 and F16, enabling a resolution corresponding to the edge length of the pixel of at most 10 μm of the illuminated area A.

42. The apparatus according to claim 31, which further comprises a guide rail configured to stabilize the fibrous material web in a position.

Description

[0060] In the following, the invention is explained in more detail on the basis of schematic figures, which are not to scale.

[0061] FIG. 1 schematically shows a section through an apparatus for determining the fiber orientation according to one aspect of the invention

[0062] FIG. 2 shows, in partial FIGS. 2a, 2b, 2c, a possible embodiment for illumination means for use in an apparatus according to one aspect of the invention.

[0063] FIG. 1 shows a fibrous material web 1, for example, a paper web 1 or a packaging web 1, which is moved in the machine direction MD. The speed of the fibrous material web 1 can be greater than 1000 m/min, in particular more than 1200 m/min here. A camera 2 is provided to record a digital image of an area A of a surface of the fibrous material web 1. In the embodiment shown in FIG. 1, an image of the lower side is recorded here. Alternatively or additionally, a camera 2 can also be arranged above the fibrous material web 1 to record an image of the upper side. Furthermore, illumination means 3 are provided to illuminate the surface of the fibrous material web 1. The illuminated area comprises the area A, which is acquired by means of the camera 2. The area A advantageously comprises a square of 5 mm×5 mm, in particular of 10 mm×10 mm. The recorded area does not have to be a square here. In tests, for example, pictures of 11 mm×9 mm were successfully prepared.

[0064] The illumination means 3 comprise a plurality of light sources 4. These light sources 4 are embodied in FIG. 1 as LEDs 4, which are arranged uniformly and annularly around the camera 2. As described, an odd number of light sources 4 is advantageous.

[0065] The illumination means 3 are embodied here so that the light of the light sources 4 is incident at an angle α—measured from the perpendicular— on the surface of the paper web 1. This angle α is advantageously <45°, that is to say the light is incident comparatively steeply on the surface. This prevents shadows on the surface topography from corrupting the measurement result, for example.

[0066] The illumination means 3 are moreover configured to illuminate the area A, of which a digital image is recorded, for a time period Δt of at most 1 [μs], in particular of 500 [ns] or less. Significantly shorter illumination times of 200 [ns] or less are even implementable with acceptable expenditure using the current technology.

[0067] In the embodiment of FIG. 1, the apparatus has a housing 6, for example, of a box made of metal. This housing 6 forms the outer wall of the sensor unit. A plate 5 is provided in the housing 6, which can consist of glass or plastic, for example, and which is entirely or largely transparent to the light of the light sources 4. The fibrous material web 1 is illuminated and also the digital image is recorded through this plate 5. To remove soiling which can accumulate on the plate 5, cleaning devices can moreover also be provided, for example, nozzles for flushing the plate 5 using air or water. These cleaning devices are not explicitly shown in FIG. 1.

[0068] In the embodiment of FIG. 1, the processing unit 7 is arranged within the sensor unit, thus in the interior of the housing 6. Furthermore, a transfer device 8 is provided to transfer data from the processing unit 7 to a receiving station which is arranged outside the actual paper machine. Since in this embodiment the calculation of the fiber orientation is carried out by the processing unit 7 in the interior of the sensor unit, the transfer device 8 only has to transfer very small amounts of data.

[0069] FIG. 2, or partial FIGS. 2a, 2b, and 2c, show details of illumination means 3, which can in particular also be used in the embodiment shown in FIG. 1. Illumination means 3 of this type moreover also represent an inventive concept alone and can be used in other fields independently of the use for determining the fiber orientation.

[0070] A printed circuit board 30 represents a central element of these illumination means 3. In the top view of FIG. 2a, it can be seen that this printed circuit board 30 is embodied in the form of a flower. A recess 32 for the camera 2 is provided in the center of the printed circuit board 30. Around the center, 15 “flower petals” 33 are arranged symmetrically. These flower petals 33 are parts of the printed circuit board 30 which are each connected via a flexible connection 31 to the center. These flower petals 33 are advantageously all embodied identically. They each comprise a light source 14. For example, “Oslon SSL 80” LEDs from Osram are suitable as the light source.

[0071] Via the flexible connection, the flower petals 33 can be set so that the light of the light sources 14 is incident at the desired angle α on the fibrous material web 1. FIG. 2b shows in perspective the printed circuit board 30 of FIG. 2a, in which the flower petals 33 were already inclined at the flexible connection 31. As described, the angle is to be less than 45°. FIG. 2c shows a section through FIG. 2b along line B. In the embodiment shown in FIG. 2, the flower petals were set at an angle α between 36° and 37°.

LIST OF REFERENCE SIGNS

[0072] 1 fibrous material web

[0073] 2 camera

[0074] 3 illumination means

[0075] 4 light source

[0076] 5 plate

[0077] 6 housing

[0078] 7 processing unit

[0079] 8 transfer device

[0080] 30 printed circuit board

[0081] 31 flexible connection

[0082] 32 recess

[0083] 33 “flower petal”

[0084] A image area

[0085] MD machine direction