METHOD AND DEVICE FOR SORTING SILICON FRAGMENTS

Abstract

Methods and devices for sorting silicon fragments. The method includes the steps of singulating the chunks in a singulating region and recording the projected area of a chunk in a 2D profile plane with at least one first measuring device. Recording at least one height information item above and/or below the 2D profile plane with at least one further measuring device. Calculating the size of the chunk from the projected area and the height information item and controlling at least one deflecting device as a function of the calculated size.

Claims

1-14. (canceled)

15. Method for sorting chunks, comprising the steps of: singulating the chunks in a singulating region; recording the projected area of a chunk in a 2D profile plane with at least one first measuring device; recording at least one height information item above and/or below the 2D profile plane with at least one further measuring device; calculating the size of the chunk from the projected area and the height information item; and controlling at least one deflecting device as a function of the calculated size.

16. The method of claim 15, wherein the first measuring device and at least one of the further measuring devices are photoelectric transmitted-light or reflected-light measuring systems having a detection region through which the chunk passes.

17. The method of claim 16, wherein the silicon chunk passes through the detection region in freefall.

18. The method of claim 16, wherein the reflected-light measuring system comprises a light section sensor and/or at least one camera system.

19. The method of claim 18, wherein the camera system is a camera system for photometric stereo analysis.

20. The method of claim 16, wherein the transmitted-light measuring system comprises a photoelectric barrier, a light curtain or a light grid.

21. The method of claim 15, wherein the first measuring device is a camera system.

22. The method of claim 15, wherein the at least one further measuring device is a light curtain or a light grid.

23. The method of claim 15, wherein the recording of the projected area and the recording of the height information item take place with a time spacing of from 0 to 100 ms, preferentially from 0 to 50 ms, particularly preferentially simultaneously.

24. The method of claim 15, wherein the deflecting device is a pneumatic or mechanical deflecting device.

25. Device for sorting chunks, comprising: a singulating region for singulating the chunks; at least one first measuring device for recording the projected area of a chunk in a 2D profile plane; at least one further measuring device for recording a height information item above and/or below the 2D profile plane; at least one deflecting device; and a software-aided controller which calculates a size of the chunk from the projected area and the height information item and controls the deflecting device as a function of this size.

26. The device of claim 25, wherein the singulating region comprises at least one vibrating conveyor trough and/or conveyor belt.

27. The device of claim 25, wherein the deflecting device is a pneumatic or mechanical deflecting device.

28. The device of claim 27, wherein the pneumatic deflecting device comprises a row or a matrix of individual nozzles.

Description

[0048] In respect of the measuring devices and the evaluation device, reference may be made to the comments above and to EP 0 983 804 A1.

[0049] FIG. 1: Device according to the invention having a light grid (transmitted-light measuring system).

[0050] FIG. 2: Device according to the invention having a light section sensor (reflected-light measuring system).

LIST OF REFERENCES USED

[0051] 10 vibrating conveyor belt [0052] 12 movement arrow [0053] 20 sliding surface [0054] 22 end of the sliding surface [0055] 30 chunk [0056] 32 projected area [0057] 40 camera [0058] 42 light source [0059] 44 detection region [0060] 50 light grid [0061] 52 emitter strip [0062] 54 IR beam path [0063] 56 receiver strip [0064] 60 light section sensor [0065] 62 laser scanner [0066] 63 static laser line [0067] 64 reception optics [0068] 65 reflected light [0069] 70 deflecting device [0070] 80 first collection container [0071] 81 separating element [0072] 82 second collection container [0073] 90 evaluation device [0074] 100 sorting device [0075] 200 sorting device

[0076] FIG. 1 shows a sorting device 100, which comprises a vibrating conveyor belt 10 as a singulating region and an oblique sliding surface 20. The forward feed direction of singulated chunks 30 is indicated by means of movement arrows 12.

[0077] As a first measuring device, a camera 40 having an external light source 42 is arranged underneath the sliding surface 20. The camera 40 is, for example, a CCD camera having an optical resolution of from 0.05 to 2.0 mm. The light source 42 is, for example, an LED having diffuse area illumination. A detection region 44 of the first measuring device, in relation to the chunk 30, is indicated as a star. As a further measuring device, a light grid 50 is fitted at a lower end 22 of the sliding surface 20. It consists of an emitter strip 52 having a total of five infrared light sources (laser or LED light sources or light dots in the visible range may also be envisaged), the radiation of which is respectively indicated by a dashed line 54, and a receiver strip 56 which correspondingly has five sensors. Underneath the first measuring device there is a pneumatic deflecting device 70, and underneath the latter there are a first and a second collection container 80, 82. The collection containers 80, 82 are connected to one another by a separating element 81 which is triangular in cross section. Furthermore, both the sensor strip 56 of the first measuring device, the camera 40 and the light source 42 of the second measuring device, as well as the deflecting device 70 are connected to an evaluation device 90. The evaluation device is a computer with image processing software, for example MATLAB.

[0078] When a chunk 30, for example a pyramidal chunk, singulated by the shaking movement of the vibrating conveyor belt 10, now reaches the oblique sliding surface 20, it becomes oriented in such a way that its centre of gravity lies as low as possible. This may generally be adapted to the chunk size of the chunks by a sliding surface 20 that is adjustable in its angle. After the end of the sliding surface 22, the chunk 30 passes through the light grid 50 in such a way that its elongated side faces in the z direction, and it is thus recorded in its full length by the light grid 50. The chunk 30 subsequently passes in freefall through the detection region 44 of the camera 40, the latter only recording a projected area 32 corresponding to the base face of the chunk 30. From the two information items, i.e. the projected area 32 and the height information item acquired by the light grid 50, the evaluation device 90 calculates the size of the chunk 30 and forwards this information to the pneumatic deflecting device 70, undeflected chunks 30 being collected in the second collection container 82 and the chunks 30 deflected by a pneumatic pulse being collected in the first collection container 82. The separating element 81 facilitates this separation.

[0079] FIG. 2 shows a further sorting device 200 according to the invention, which corresponds substantially to the sorting device of FIG. 1 (elements which correspond to one another have corresponding references; the representation of the evaluation device, deflecting device and collection containers has been omitted). The sorting device 200 has a light section sensor 60 as a further measuring device. It consists of a laser projector 62 and reception optics 64. The light section sensor 60 uses the triangulation principle to ascertain the height information item (3D profile recording). By means of special optics, a laser beam is broadened to form a laser line 63 (represented by the finely dashed lines) and projected onto the surface of the chunk 30 passing through. The reception optics 64 image the light 65 reflected by the surface (this light being represented by the coarsely dashed lines) on a sensor matrix. An evaluation device (not shown) connected to the light section sensor 60 can calculate the height information item of the chunk passing through (z axis) from the acquired matrix image along the laser line (x axis). This information item may then be output in a two-dimensional coordinate system which is fixed with respect to the sensor. In the case of moving objects or when crossing the sensor, 3D measurement values may additionally be acquired.

COMPARATIVE EXAMPLE 1

[0080] Classification of comminuted (crushed) polysilicon having a chunk size (CS) 2.

[0081] The size class of polysilicon chunks is defined as the longest distance between two points on the surface of a silicon chunk (corresponding to the maximum length):

TABLE-US-00001 CS0 0.1 to 5 mm CS1 3 to 15 mm CS2 10 to 40 mm CS3 20 to 60 mm CS4 45 to 120 mm CS5 100 to 250 mm

[0082] The polysilicon sample material used for the test was produced from a mixture of 9000 chunks in the length range of from 10 to 40 mm (CS2) and 1000 chunks in the length range >40 to 65 mm, namely the fraction to be separated. In order to prepare the sample material, a mechanical screening method (analysis screen according to DIN ISO 3310-2 with a normal hole width W=4 mm (square perforation)) was used to remove the chunk fractions of from 0 to 10 mm. The maximum length both of the chunks in the length range of from 10 to 40 mm and of the chunks of the fraction to be separated in the length range of from 40 to 65 mm was determined manually (vernier calliper) and the polysilicon sample material was then mixed.

[0083] This polysilicon sample material was subjected to conventional optopneumatic sorting of the fraction >40 mm.

[0084] The optopneumatic sorting device used was equipped with a first 2D measuring device (CCD camera and light source according to FIG. 1) for recording a projected area of the chunks. The chunks passed through the detection region of the measuring device individually (conventionally with a distance of 0.5-10 mm between the chunks) over an oblique sliding plane. The measuring device was coupled to an evaluation device at a process control station. The deflecting device, comprising an approximately 50 cm wide nozzle strip having two rows of 100 nozzles each, was also connected to this control station. A separating interval of 40 mm was set at the control station.

[0085] At the end of the sorting, the slippage of the separating method was determined by manual analysis (vernier calliper) in conjunction with manual counting of the chunks. It was 0.1%.

EXAMPLE 1

[0086] The polysilicon sample material described in the comparative example was separated with an optopneumatic sorting device having substantially the same design (with a separating interval of 40 mm). In contrast to Comparative Example 1, however, the device had a second 2D measuring device. This was a light grid as described with reference to FIG. 1.

[0087] One possible way of evaluating the information items acquired by the measuring devices is presented below, this having been carried out with MATLAB (from the company Math Works). [0088] The image recording with the first measuring device is configured as a row of sensors and, per unit of time, delivers the shadow cast by the chunks as a vector x with greyscale values [0 . . . 255]. [0089] At the same time, a value of the height information item is recorded with the second measuring device: scalar z in [mm]. [0090] The individual measurements are combined as a function of time t to form an image: image [x,y] with greyscale values [0 . . . 255, 0 . . . 255]. [0091] The height information items are combined as a function of time t to form a vector and are assigned to the ordinate: vector [z] with values in [mm]. [0092] Repeated evaluation of the images formed in this way is carried out. [0093] By means of an adjustable greyscale value (for example the greyscale value 128), the greyscale values [0 . . . 255] are converted into binary values [0=dark or 1=bright]. [0094] By searching for continuous regions with [0=dark] in the image, a list of chunks is acquired. [0095] Repeated calculation is carried out for each chunk. [0096] Calculation of the points at the edge of the region as a list and conversion into [mm]: list [xi,yi] in [mm]. [0097] Allocation of the height values to the list: [xi,yi,zi] in [mm]. [0098] Calculation of the maximum distance in 3D for all points of the list [xi,yi,zi] with respect to one another: scalar for the maximum extent in [mm] of the chunk. [0099] If an adjustable limit value in [mm] for the maximum extent of the chunk is exceeded, an instruction is given to blow out the chunk in the region of the nozzle strip in which the chunk is located [min(xi), max(xi)].

[0100] The slippage after this sorting was manually established as described above, and was 0.0%.

COMPARATIVE EXAMPLE 2

[0101] Classification of comminuted polysilicon in CS3.

[0102] First, polysilicon sample material consisting of 9000 chunks in a length range of from 20 to 60 mm (CS3) and 1000 chunks in a length range >60 to 85 mm (the fraction to be separated) was produced.

[0103] The verification of the chunk lengths was carried out manually. Following this, the polysilicon sample material was made up by mixing.

[0104] The polysilicon sample material was sorted with the optopneumatic sorting device described in Comparative Example 1, but with a separating interval of 60 mm.

[0105] The slippage after this sorting was manually established as described above, and was 1.0%.

EXAMPLE 2

[0106] The polysilicon sample material described in Comparative Example 2 was in this case sorted with an optopneumatic sorting device according to FIG. 2. It thus had a second measuring device in the form of a light section sensor consisting of a laser projector and reception optics.

[0107] The slippage after this sorting was manually established as described above, and was 0.0%.

[0108] It was possible to show that the sorting outcome can be significantly improved, particularly in the case of pyramidal objects, by an additional height information item determined by means of a second measuring device. The aim of any sorting is essentially a clean separating interval without slippage in respect of a chunk size.