METAL SCRAP SORTING SYSTEM

• US 20030034281A1
• Filed: 06/15/2001
• Published: 02/20/2003
• Est. Priority Date: 02/16/1996
• Status: Active Grant

• Current Assignee: Huron Valley Steel Corporation
• Original Assignee: Huron Valley Steel Corporation
• Inventors: Kumar, Pradeep
• Granted Patent: US 6,545,240 B2
• Time in Patent Office: Days
• US Class Current: 209/579
• CPC Class Codes: B07C 2501/0054 Sorting of waste or refuse
• CPC Class Codes: B07C 5/3425 of granular material, e.g. ore particles, grain investigation moving fluids or granular solids using optical means G01N21/85
• CPC Class Codes: B07C 5/366 during free fall of the articles
• CPC Class Codes: G01N 21/718 Laser microanalysis, i.e. with formation of sample plasma

Abstract

A system for sorting randomly positioned, irregularly shaped scrap metal particles on a moving conveyor employs laser-induced breakdown spectroscopy (LIBS), and includes an image detector for locating the particles as they path through a predefined viewing area, a position detector for detecting movement of the conveyor, a laser system for providing laser pulses, a scanner assembly for directing the pulses to selected locations within a target area, a light collector, a light distribution and spectral analyzer for isolating and measuring at least one selected band from the collected light, a separator, and suitable logic for identifying the particles, monitoring their position, monitoring the output of the laser and, operating the scanner assembly to direct the pulses to the identified particle. The spectral data is then analyzed, each particle is categorized, and thereafter sorted.

Claims

1. A system for sorting randomly positioned scrap particles on a moving conveyor, the system including:

an image detector for locating scrap particles as they pass through a predefined viewing area on the conveyor;

a position detector for detecting movement of the conveyor;

a laser system including at least one laser to periodically provide a laser beam including a plurality of laser pulses within a selected time interval;

at least one target scanner assembly mounted to direct focused laser pulses to a selected location within a two-dimensional target area on the conveyor downstream from the viewing area, said at least one target scanner assembly including a beam deflector mounted in the path of the laser pulses, and a focusing element mounted in the path of the laser pulses downstream from the beam deflector to focus the laser pulses and provide a generally uniform power density from the pulses along a plane;

a light collector for receiving light in the target area from plasma generated by said laser pulses;

a light distribution and spectral analyzer system for isolating and measuring at least one selected band from the light collected by the light collector, the light distribution and spectral analyzer system including at least one spectral filter operably connected to the light collector to transmit a band of selected frequency to a detector which provides a signal corresponding to the intensity of the emission of the spectral filter;

a separator; and

a control including logic for processing the image data acquired from the image detector to identify scrap particles as the particles pass through the viewing area on the moving conveyor, continuously monitoring the positions of each of the identified particles on the moving conveyor based on information received from the position detector, continuously monitoring the laser system to determine when the next plurality of pulses will be produced, and when pulses are available, locating a scrap particle at least one target area, generating the control signals necessary to operate the at least one target scanner assembly to direct the next plurality of pulses to irradiate the located scrap particle, wherein the selected time interval of the pulses allows each pulse to strike the particle without re-positioning the beam deflector in the scanner assembly, analyzing the spectral data thereafter received from the target location, generating a discriminator signal based on the results of the spectral data analysis, and selectively activating the separator as a function of the discriminator signal to sort the scrap particles.

2. The system of claim 1 wherein the laser system includes two solid-state fixed frequency lasers synchronized to periodically provide the plurality of laser pulses within the selected time interval.

3. The system of claim 2 wherein each of the lasers in the laser system are operating in double-pulse mode.

4. The system of claim 2 wherein the lasers are capable of generating at least four pulses within the selected time interval.

5. The system of claim 1 wherein the selected time interval is less than about 250 microseconds.

6. The system of claim 1 wherein the beam deflector comprises at least two galvanometric scanners, each scanner including a positionable mirror, each of the mirrors mounted in the path of the laser pulses.

7. The system of claim 1 wherein the focusing element comprises an F-Theta lens.

8. The system of claim 1 wherein the focusing element comprises an F-Theta telecentric lens.

9. The system of claim 1 wherein the spectral filter includes at least one monochromater.

10. The system of claim 1 wherein the spectral filter includes a polychromater.

11. The system of claim 1 wherein the detector is a photomultiplier tube.

12. The system of claim 1 wherein the signal provided by the detector is acquired by the control using a high speed analog-to-digital converter.

13. The system of claim 1 wherein a plurality of target scanner assemblies are utilized, and wherein the combined target areas of the target scanner assemblies cover substantially the entire width of the conveyor.

14. The system of claim 1 wherein the light collector includes a plurality of optical fibers.

15. The system of claim 1 wherein the image detector includes a linescan camera and a light system which provides uniform illumination of the viewing area.

16. The system of claim 15 wherein the position detector is an encoder, and wherein the linescan camera acquires a linescan of the viewing area at each pulse of the encoder.

17. The system of claim 1 wherein the separator comprises a plurality of air nozzles generally equally spaced across the width of the conveyor, which air nozzles may be selectively and independently controlled to provide an air blast at a selected time to urge a selected scrap particle into a desired path.

18. The system of claim 1 wherein the separator comprises a plurality of air nozzle assemblies, each air nozzle assembly comprising a plurality of air nozzles generally equally spaced across the width of the conveyor, which air nozzles may be selectively and independently controlled to provide an air blast at a selected time to urge a selected scrap particle into a selected path, and wherein the selected path of each of the air nozzle assemblies is different, whereby the scrap particles may be sorted into a plurality of categories.

19. The system of claim 18 wherein the separator comprises three air nozzle assemblies mounted for separating the particles into four separate categories.

20. The system of claim 1 wherein the logic employs a ratioing regime for analyzing the spectral data received from the target location.

21. The system of claim 1 wherein the logic employs a neural network for analyzing the spectral data received from the target location.

22. The system of claim 21 wherein the neural network receives other data inputs in addition to the spectral data inputs.

23. The system of claim 22 wherein the other data inputs include data corresponding to laser energy scattered and laser energy produced in connection with each particle.

24. The system of claim 22 wherein the other data inputs include image data relating to each of the particles.

25. The system of claim 1 wherein the control logic includes logic for analyzing image information relating to a particle, and wherein the logic for generating a discriminator signal is based upon the image data analysis as well as the spectral data analysis for a particle.

26. The system of claim 1 wherein the control includes hardware comprising a plurality of processors that are networked to provide the capability for simultaneous processing of multiple control functions.

27. A system for sorting randomly positioned scrap metal particles on a moving conveyor including:

an image detector for locating scrap particles as they pass through a predefined viewing area on the conveyor;

a position detector for detecting movement of the conveyor;

a laser pool comprising a plurality of laser systems, each laser system including at least one laser to periodically provide a laser beam including a plurality of laser pulses within a selected time interval;

at least one target scanner assembly, said at least one target scanner assembly mounted to direct the laser pulses to a selected location within a two-dimensional target area on the conveyor downstream from the viewing area, said at least one target scanner assembly including a beam deflector mounted in the path of the laser pulses, and a focusing element mounted in the path of the laser pulses downstream from the beam deflector to focus the laser pulses and provide a generally uniform power density from the pulses along a plane;

a light collector associated with said at least one target scanner assembly, the light collector mounted to receive light from plasma generated by said laser pulses in the target area of the associated scanner assembly;

a light distribution and spectral analyzer system for isolating and measuring at least one selected band from the light collected by the light collector, the light distribution and spectral analyzer system including at least one spectral filter operably connected to the light collector to transmit a band of selected frequency to a detector which provides a signal corresponding to the intensity of the emission of the spectral filter;

a separator; and

a control including logic for processing the image data acquired from the image detector to identify scrap particles as the particles pass through the viewing area on the moving conveyor, continuously monitoring the positions of each of the identified particles on the moving conveyor based on information received from the position detector, continuously monitoring each laser system in the pool to determine when the next plurality of pulses will be produced, and when pulses are available, locating a scrap particle in at least one target area, generating the control signals necessary to operate the at least one target scanner assembly to direct the next plurality of pulses to irradiate the located scrap particle, wherein the selected time interval allows each pulse to strike the particle without repositioning the beam deflector in the scanner assembly, analyzing the spectral data thereafter received from the target location, generating a discriminator signal based on the results of the spectral data analysis, and selectively activating the separator as a function of the discriminator signal to sort the scrap particles.

28. The system of claim 27 wherein each laser system includes two solid-state fixed frequency lasers synchronized to periodically provide the plurality of laser pulses within the selected time interval.

29. The system of claim 28 wherein each of the lasers in each laser system are operating in double-pulse mode.

30. The system of claim 28 wherein the lasers are capable of generating at least four pulses within the selected time interval.

31. The system of claim 27 wherein the selected time interval is less than about 250 microseconds.

32. The system of claim 27 wherein the beam deflector comprises at least two galvanometric scanners, each scanner including a positionable mirror, each of the mirrors mounted in the path of the laser pulses.

33. The system of claim 27 wherein the focusing element comprises an F-Theta lens.

34. The system of claim 27 wherein the focusing element comprises an F-Theta telecentric lens.

35. The system of claim 27 wherein the spectral filter includes at least one monochromater.

36. The system of claim 27 wherein the spectral filter includes a polychromater.

37. The system of claim 27 wherein the detector is a photomultiplier tube.

38. The system of claim 27 wherein the signal provided by the detector is acquired by the control using a high speed analog-to-digital converter.

39. The system of claim 27 wherein a plurality of target scanner assemblies are utilized, and wherein the combined target areas of the target scanner assemblies cover substantially the entire width of the conveyor.

40. The system of claim 27 wherein the light collector includes a plurality of optical fibers.

41. The system of claim 27 wherein the image detector includes a linescan camera and a light system which provides uniform illumination of the viewing area.

42. The system of claim 41 wherein the position detector is an encoder, and wherein the linescan camera acquires a linescan of the viewing area at each pulse of the encoder.

43. The system of claim 27 wherein the separator comprises a plurality of air nozzles extending across the width of the conveyor, which air nozzles may be selectively and independently controlled to provide an air blast at a selected time to urge a selected scrap particle into a desired path.

44. The system of claim 27 wherein the separator comprises a plurality of air nozzle assemblies, each air nozzle assembly comprising a plurality of air nozzles generally equally spaced across the width of the conveyor, which air nozzles may be selectively and independently controlled to provide an air blast at a selected time to urge a selected scrap particle into a selected path, and wherein the selected path of each of the air nozzle assemblies is different, whereby the scrap particles may be sorted into a plurality of categories.

45. The system of claim 44 wherein the separator comprises three air nozzle assemblies mounted for separating the particles into four separate categories.

46. The system of claim 27 wherein the logic employs a ratioing regime for analyzing the spectral data received from the target location.

47. The system of claim 27 wherein the logic employs a neural network for analyzing the spectral data received from the target location.

48. The system of claim 47 wherein the neural network receives other data inputs in addition to the spectral data inputs.

49. The system of claim 48 wherein the other data inputs include data corresponding to laser energy scattered and laser energy produced in connection with each particle.

50. The system of claim 48 wherein the other data inputs include image data relating to each of the particles.

51. The system of claim 27 wherein the control logic includes logic for analyzing image information relating to a particle, and wherein the logic for generating a discriminator signal is based upon the image data analysis as well as the spectral data analysis for a particle.

52. The system of claim 27 wherein the control includes hardware comprising a plurality of processors that are networked to provide the capability for simultaneous processing of multiple control functions.

53. A system for sorting randomly positioned scrap metal particles on a moving conveyor, the system including:

an image detector for locating scrap particles as they pass through a predefined viewing area on the conveyor, the image detector including a linescan camera and a light system which provides uniform illumination of the viewing area;

a position detector for detecting movement of the conveyor;

a laser system including at least one solid-state fixed frequency laser configured to periodically provide a laser beam including a plurality of laser pulses within a selected time interval;

a plurality of target scanner assemblies, each target scanner assembly mounted to direct focused laser pulses to a selected location within a two-dimensional target area on the conveyor downstream from the viewing area, each target scanner assembly including a beam deflector comprising at least two galvanometric scanners, each scanner including a positionable mirror, each of the mirrors mounted in the path of the laser pulses, and a focusing element comprising an F-Theta lens mounted in the path of the laser pulses downstream from the beam deflector to focus the laser pulses and provide a generally uniform power density from the pulses along a plane, wherein the combined target areas of the target scanner assemblies cover substantially the entire width of the conveyor;

a light collector including a plurality of optical fibers for receiving light in the target areas from plasma generated by said laser pulses;

a light distribution and spectral analyzer system for isolating and measuring at least one selected band from the light collected by the light collector, the light distribution and spectral analyzer system including a spectral filter having at least one monochromater operably connected to the light collector to transmit band of selected frequency to a detector which provides a signal corresponding to the intensity of the emission of the spectral filter;

a separator; and

a control including logic for processing the image data acquired from the image detector to identify scrap particles as the particles pass through the viewing area on the moving conveyor, continuously monitoring the positions of each of the identified particles on the moving conveyor based on information received from the position detector, continuously monitoring the laser system to determine when the next plurality of pulses will be produced, and when pulses are available, locating a scrap particle in one of the target areas, generating the control signals necessary to operate the appropriate target scanner assembly to direct the next plurality of pulses to irradiate the located scrap particle, wherein the selected time interval of the pulses allows each pulse to strike the particle without re-positioning the mirrors in the scanner assembly, analyzing the spectral data thereafter received from the target location, generating a discriminator signal based on the results of the spectral data analysis, and selectively activating the separator as a function of the discriminator signal to sort the scrap particles.

54. A method for sorting randomly positioned scrap particles on a moving conveyor in a system including, the method including;

locating scrap particles as they pass through a predefined viewing area on the conveyor by periodically acquiring a digital image of the viewing area;

detecting movement of the conveyor;

providing a laser system including at least one laser to periodically provide a laser beam including a plurality of laser pulses within a selected time interval;

directing focused laser pulses to a selected location within a two-dimensional target area on the conveyor downstream from the viewing area, using at least one target scanner assembly including a beam deflector mounted in the path of the laser pulses, and a focusing element mounted in the path of the laser pulses downstream from the beam deflector to focus the laser pulses and provide a generally uniform power density from the pulses along a plane;

collecting light in the target area from the generated plasma;

isolating and measuring at least one selected band from the collected light using a light distribution and spectral analyzer system including at least one spectral filter operably connected to the light collector to transmit a band of selected frequency to a detector which provides a signal corresponding to the intensity of the emission of the spectral filter;

providing an actuable separator for selectively directing the particles along different sort paths as they reach the end of the conveyor; and

processing each acquired image to identify scrap particles as the particles pass through the viewing area on the moving conveyor, continuously monitoring the positions of each of the identified particles on the moving conveyor based on the detected movement of the conveyor, continuously monitoring the laser system to determine when the next plurality of pulses will be produced, and when pulses are available, operating at least one target scanner assembly to direct the next available plurality of pulses to irradiate an identified scrap particle, wherein the selected time interval of the pulses allows each pulse to strike the particle without re-positioning the beam deflector in the scanner assembly, analyzing the spectral data thereafter received from the target location, and selectively activating the separator based on the results of the spectral data analysis to sort the scrap particles.

56. The method of claim 54 wherein the laser beam is provided to include at least four pulses within a time interval of about 250 microseconds.

57. The method of claim 54 wherein analyzing the spectral data includes employing a ratioing regime.

58. The method of claim 54 wherein analyzing the spectral data includes employing a neural network.

59. The method of claim 54 further including analyzing image data relating to a selected particle, and wherein the separator is selectively activated based upon the results of the image data analysis as well as the spectral data analysis.

55. A system for sorting randomly positioned scrap particles on a moving conveyor, the system including:

an image detector for locating scrap particles as they pass through a predefined viewing area on the conveyor;

a position detector for detecting movement of the conveyor;

a laser system including a laser to periodically provide a laser beam including a plurality of laser pulses within a selected time interval;

a target scanner assembly mounted to direct focused laser pulses to a selected location within a two-dimensional target area on the conveyor downstream from the viewing area;

a light collector for receiving light in the target area from the plasma generated by said laser pulses;

a light distribution and spectral analyzer system for isolating and measuring at least one selected band from the light collected by the light collector;

a separator; and

a control including logic for processing the image data acquired from the image detector to identify scrap particles as the particles pass through the viewing area on the moving conveyor, monitoring the positions of each of the identified particles on the moving conveyor based on information received from the position detector, monitoring the laser system to determine when the next plurality of pulses will be produced, and when pulses are available, locating a scrap particle in the target area, generating the control signals necessary to operate the target scanner assembly to direct the next plurality of pulses to irradiate the located scrap particle, wherein the selected time interval of the pulses allows each pulse to strike the particle without re-positioning the beam deflector in the scanner assembly, analyzing the spectral data thereafter received from the target location, generating a discriminator signal based on the results of the spectral data analysis, and selectively activating the separator as a function of the discriminator signal to sort the scrap particles.

60. A method for sorting randomly positioned scrap particles on a moving conveyor, the method including;

locating scrap particles as they pass through a predefined viewing area on the conveyor by periodically acquiring a digital image of the viewing area;

detecting movement of the conveyor;

providing a laser system including at least one laser to periodically provide a laser beam including a plurality of laser pulses within a selected time interval;

directing focused laser pulses to a selected location within a two-dimensional target area on the conveyor downstream from the viewing area, and focusing the laser pulses to provide a generally uniform power density from the pulses along a plane;

collecting light in the target area from the generated plasma;

isolating and measuring at least one selected band from the collected light, and providing a signal corresponding to the intensity of the emission of the selected band;

providing an actuable separator for selectively directing the particles along different sort paths as they reach the end of the conveyor; and

processing each acquired image to identify scrap particles as the particles pass through the viewing area on the moving conveyor, continuously monitoring the positions of each of the identified particles on the moving conveyor based on the detected movement of the conveyor, directing the next available plurality of pulses to irradiate an identified scrap particle, wherein the selected time interval of the pulses allows each of the plurality of pulses to strike the particle without re-directing the laser pulses, analyzing the spectral data thereafter received from the target location by employing a neural network to perform at least part of the analysis, and selectively activating the separator based on the results of the spectral data analysis to sort the scrap particles.