APPARATUS FOR CONVEYING A PRODUCT STREAM OF CHUNK POLYSILICON OR GRANULAR POLYSILICON

Abstract

Foreign objects in a conveyed product stream of granular or chunk polysilicon is effected by identifying the foreign objects by eddy current sensors in the conveyor by which the granular or chunk polysilicon is being conveyed.

Claims

1.-8. (canceled)

9. An apparatus for conveying a product stream of chunk polysilicon or granular polysilicon, comprising a metal conveying surface lined with plastic or with silicon, containing eddy current sensors for detection of metallic or electrically conductive foreign objects in the product stream.

10. The apparatus of claim 9, wherein the eddy current sensors are situated in a housing below the lining of the conveying surface.

11. The apparatus of claim 10, further comprising lateral linings to which the housing and lining are clamped.

12. The apparatus of claim 9, wherein the eddy current sensors are arranged in a plurality of parallel and spaced-apart rows transversely to the product stream direction of conveyance.

13. The apparatus of claim 10, wherein the eddy current sensors are arranged in a plurality of parallel and spaced-apart rows transversely to the product stream direction of conveyance.

14. The apparatus of claim 11, wherein the eddy current sensors are arranged in a plurality of parallel and spaced-apart rows transversely to the product stream direction of conveyance.

15. The apparatus of claim 12, wherein at least one row of eddy current sensors is arranged transversely offset relative to another row of eddy current sensors.

16. The apparatus of claim 12, wherein the eddy current sensors are arranged such that a triangle having minimum side lengths S is formed when the central points of two nearest adjacent eddy current sensors of one row are connected to the central point of the common nearest adjacent eddy current sensor of an adjacent row.

17. The apparatus of claim 15, wherein the eddy current sensors are arranged such that a triangle having minimum side lengths S is formed when the central points of two nearest adjacent eddy current sensors of one row are connected to the central point of the common nearest adjacent eddy current sensor of an adjacent row.

18. A method of identifying metallic or electrically conductive foreign objects in a product stream of chunk polysilicon or granular polysilicon, wherein the product stream is moved on a plastic- or silicon-lined metallic conveying surface of an apparatus of claim 9, wherein the detection of the foreign objects is effected by means of eddy current sensors.

19. A method of identifying metallic or electrically conductive foreign objects in a product stream of chunk polysilicon or granular polysilicon, wherein the product stream is moved on a plastic- or silicon-lined metallic conveying surface of an apparatus of claim 10, wherein the detection of the foreign objects is effected by means of eddy current sensors.

20. A method of identifying metallic or electrically conductive foreign objects in a product stream of chunk polysilicon or granular polysilicon, wherein the product stream is moved on a plastic- or silicon-lined metallic conveying surface of an apparatus of claim 11, wherein the detection of the foreign objects is effected by means of eddy current sensors.

21. A method of identifying metallic or electrically conductive foreign objects in a product stream of chunk polysilicon or granular polysilicon, wherein the product stream is moved on a plastic- or silicon-lined metallic conveying surface of an apparatus of claim 12, wherein the detection of the foreign objects is effected by means of eddy current sensors.

22. A method of identifying metallic or electrically conductive foreign objects in a product stream of chunk polysilicon or granular polysilicon, wherein the product stream is moved on a plastic- or silicon-lined metallic conveying surface of an apparatus of claim 15, wherein the detection of the foreign objects is effected by means of eddy current sensors.

23. A method of identifying metallic or electrically conductive foreign. objects in a product stream of chunk polysilicon or granular polysilicon, wherein the product stream is moved on a plastic- or silicon-lined metallic conveying surface of an apparatus of claim 16, wherein the detection of the foreign objects is effected by means of eddy current sensors.

24. The method of claim 18, wherein conveying of the chunk polysilicon or granular polysilicon is interrupted via evaluation electronics when a foreign object is detected.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] FIG. 1 is a schematic diagram of a conveying channel having an integrated sensor unit comprising sensors arranged transversely to the direction of conveyance in two rows.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] In principle any plant (even metallic plants) used in the production of polysilicon may be retrofitted with such an apparatus in relatively simple fashion. Existing plants or lining materials need not be adapted. Use of the apparatus according to the invention does not impair polysilicon purity.

[0028] In one embodiment the conveying device is a conventional transport channel or plant, preferably a vibratory conveying channel, comprising a conveying trough or channel trough which forms the conveying surface and is lined with plastic or silicon. The lining serves to protect the polysilicon product stream moved on the conveying or channel trough from contamination, especially since the conveying surface is made of metal.

[0029] In one embodiment the eddy current sensors for detection of the foreign objects are installed directly in the conveying or channel trough, namely below the plastic or silicon lining thereof.

[0030] In one embodiment the eddy current sensors have a modular construction comprising a housing top section, a housing middle section and a housing bottom section. The sensors may be secured in the housing middle section. The cabling for the sensors is passed into the housing via the housing bottom section. The housing top section serves to cover the sensors. The lining of the conveying or channel trough may also be secured to the housing top section. The modular construction of the housing makes it easier to change the sensors, housing sections etc. The housing bottom section may comprise a welded-in stainless steel plate for equalizing the sensors and a plurality of cable entry ports. The cable entry ports serve to pass the sensor cable into the housing. The middle housing section serves to secure the sensors and to embed the sensor cables. The housing top section is arranged immediately above the sensors and serves to cover the sensors and to secure the lining. The 3-piece housing is preferably assembled in a dust-tight fashion by means of screw connections.

[0031] In a preferred embodiment the eddy current sensors are secured in a single-piece electrically nonconductive housing. The detection surface of the sensor is preferably protected by a highly-resistant nonconductive material on wear and contamination grounds. The lining of the conveying or channel trough may additionally be secured to the housing. Changing of the sensor means may be carried out individually without disassembly of the housing from the underside of the conveying unit.

[0032] In another embodiment the housing is a dust-impermeable plastic housing.

[0033] In one embodiment, lateral linings of the conveying or channel trough are also present. The linings are made of nonconductive materials, for example plastic, silicon or ceramic. The use of polyurethane (PU) is preferred.

[0034] In one embodiment a plurality of eddy current sensors are arranged in a row and transversely to the direction of the product stream. In another, preferred, embodiment a plurality of eddy current sensors are arranged in a plurality of rows offset relative to one another transversely and in the direction of the product stream.

[0035] In order to avoid interference a certain minimum distance S between nearest adjacent sensors should be present.

[0036] In one embodiment two or more parallel rows of eddy current sensors are arranged transversely to the direction of conveyance.

[0037] On account of the mutual field influencing, the minimum distance S must be maintained between the individual sensors as a function of the sensor intensity. The nearest adjacent sensors of the second row must likewise maintain the minimum distance S, there being at least a distance S to the sensors of the first row.

[0038] The detection accuracy of the apparatus may be varied by means of the offset angle a of the sensor rows, while observing the minimum distance S between one another, and the number thereof.

[0039] The detection accuracy may moreover be increased via an only small distance between the central axis of the sensor and the central axis of the foreign object. The highest accuracy is achieved via a distance=0.

[0040] In one embodiment the conveying device is switched off via evaluation electronics when a foreign object is detected.

[0041] In one embodiment the housing with the sensors situated therein is mounted to the conveying or channel trough of the conveying device. The housing is situated below the lining of the conveying or channel trough. Securing is effected by clamping to the lateral lining parts.

[0042] In one embodiment the housing is made of plastic, preferably of polyamide.

[0043] A certain distance between the sensors and the housing top section should be maintained. This ensures that the sensors are not damaged by vibrations.

[0044] The number of sensors depends on the channel width, the sensor field line intensity, the detection accuracy and reliability.

[0045] The width of the conveying surface/the channel width may be from 200 mm up to 2000 mm. In one embodiment the channel width is 400-600 mm.

[0046] The greater the conveying surface the greater the number of sensors required.

[0047] The distance S between the sensors should be chosen such that no mutual impairment of adjacent eddy current sensors occurs.

[0048] The distance S between the sensors is preferably from 30 to 200 mm and in one embodiment the distance S is 80-120 mm.

[0049] The width of the lateral lining should be chosen such that the channel trough does not interfere with the field lines.

[0050] A high detection reliability for relatively small metallic or electrically conducting foreign objects can be achieved via a sensor arrangement comprising a plurality of sensor rows, wherein the sensor rows are arranged offset relative to one another transversely to the direction of conveyance. This better covers the entire conveying surface.

[0051] On account of the interspace (distance S) between two sensors of one row a small foreign object conveyed with the product stream could remain undiscovered. However, when a second row of sensors parallel to the first row is present it is ensured that even this small foreign object will be detected. It is also possible for more than two sensor rows to be present to achieve an even better detection accuracy. The preferred number of sensor rows depends on the sensor distance S in the first row.

[0052] When a second row having sensors parallel to the first row is present it is preferable that at least the minimum distance S between the sensors be maintained.

[0053] To enhance detection accuracy more than two sensor rows offset with respect to the preceding row may also be present. The number of sensor rows is preferably up to 5. The offset of the rows relative to one another is to be implemented as a function of the required detection accuracy.

[0054] On account of different field line configurations within the detection radius of a sensor and thus over a detection row, the arrangement of a plurality of rows must be chosen such that the required detection accuracy represents the necessary detection reliability over the required width via the offsetting of subsequent rows.

[0055] Thus in one embodiment the sensor arrangement is chosen such that a triangle having the minimum side lengths S is formed when the central points of two nearest adjacent sensors of one row are connected to the central point of the common nearest adjacent sensor of another row cf. FIG. 1.

[0056] The evaluation of the eddy current sensors may be effected via a current output signal, preferably via a voltage output signal.

[0057] A change in the voltage signal brought about by a metallic or electrically conductive foreign object allows the conveying channel to be stopped via evaluation electronics.

[0058] The features cited in connection with the abovedescribed embodiments of the method according to the invention may be correspondingly applied to the apparatus according to the invention. Conversely, the features cited in connection with the abovedescribed embodiments of the apparatus according to the invention may be correspondingly applied to the method according to the invention. These and other features of the embodiments according to the invention are elucidated in the description of the figures and in the claims. The individual features can either be realized separately or in combination as embodiments of the invention. Said features may further describe advantageous implementations eligible for protection in their own right.

LIST OF REFERENCE NUMERALS EMPLOYED

[0059] 1 sensor [0060] 2 sensor intensity [0061] 3 housing [0062] 4 lining [0063] 5 channel trough [0064] offset angle

[0065] FIG. 1 shows a housing 3 which is mounted to the channel trough 5 of the transport unit and comprises sensors 1 having an intensity 2.

[0066] The distance S between the sensors 1 is chosen depending of their intensities 2 such that no mutual influencing of the sensors 1 occurs.

[0067] The housing 3 is clamped to the lining of the channel trough (not shown) via the lateral lining 4.

[0068] Also shown is the direction of conveyance in which the product stream moves.

[0069] Three rows of sensors 1 are present which are arranged in parallel and transversely to the direction of conveyance.

[0070] The nearest adjacent sensors 1 are each spaced apart from one another by the distance S.

[0071] In addition, one row is offset relative to another row transversely to the direction of conveyance by the distance S/2.

[0072] The description hereinabove of illustrative embodiments is to be understood as being exemplary. The disclosure made thereby enables a person skilled in the art to understand the present invention and the advantages associated therewith and also encompasses alterations and modifications to the described structures and methods obvious to a person skilled in the art. All such alterations and modifications and also equivalents shall therefore be covered by the scope of protection of the claims.