Method of sorting waste paper

Abstract

Apparatus and methods are provided for sensing the presence of bright white paper on a conveyor of a paper sorting system. The conveyor is constantly illuminated with ultraviolet light. When bright white paper is present in the inspection zone of the conveyor, it will re-radiate fluorescent light energy as a result of the ultraviolet light. Periodically, the inspection zone of the conveyor is illuminated with a second light source in the visible light spectrum. Light is collected from the inspection zone of the conveyor, including reflected light from the secondary source and including emitted fluorescent light energy as a result of the ultraviolet light falling on bright white paper. Periodically a microprocessor associated with the sensor senses reflected light from the second source to determine whether any object if present on the conveyor. The microprocessor then senses the level of fluorescent light energy being emitted from any object on the conveyor. The system determines first whether any object is present on the conveyor, as a result of the reflected secondary light, and then determines whether that object is bright white paper depending upon the measured level of emitted fluorescent light energy. Based upon these determinations, the stream of waste paper on the conveyor can be sorted into two fractions, one of which is the bright white paper.A method of sorting waste paper includes spreading waste paper out into a layer that is substantially one unit thick; detecting the presence or absence of a predetermined optical characteristic as the layer of paper is passed by a sensor; and controlling one or more actuators that direct a sheet of paper based on the presence or absence of the predetermined optical characteristic.

1. A method of sorting waste paper, comprising:
 spreading waste paper out into a layer that is substantially one unit thick;  
 detecting the presence or absence of a predetermined optical characteristic as the layer of paper is passed by a sensor; and  
 controlling one or more actuators that direct a sheet of paper based on the presence or absence of the predetermined optical characteristic.  
 
     
     
       2. The method of  claim 1 , wherein the predetermined optical characteristic is fluorescence caused by optical brighteners in the paper, and wherein the presence or absence of the fluorescence is detected by:
 applying ultraviolet light on a sheet of waste paper;  
 detecting light received from the paper in response to the ultraviolet light applied; and  
 comparing the level of light received from the paper with a threshold to detect the presence or absence of optical brighteners in the paper.  
 
     
     
       3. The method of  claim 1 , wherein:
   said spreading step includes carrying said layer on a conveyor having a width; and        in said detecting step, said sensor includes an array of sensor elements spaced across the width of the conveyor.     
     
     
       4. The method of  claim 3 , wherein:
   in said controlling step, said one or more actuators include one or more air jets.     
     
     
       5. The method of  claim 4 , wherein:
   in said controlling step, said one or more air jets include an array of air jets spaced across the width of the conveyor, and said controlling step includes actuating an appropriate number of said air jets at an appropriate time to direct the sheet of paper.     
     
     
       6. The method of  claim 5 , wherein:
   in said controlling step, each one of said air jets is associated with one of said sensing elements.     
     
     
       7. The method of  claim 1 , wherein:
   in said controlling step, each of said actuators includes an air jet.     
     
     
       8. The method of  claim 7 , wherein:
   said spreading step includes spreading said layer on a conveyor having a width; and        in said controlling step, said air jets comprise an array of air jets spaced across the width of the conveyor.     
     
     
       9. The method of  claim 7 , wherein:
   said detecting step includes communicating sensor signals from the sensor to a microprocessor; and        said controlling step comprises communicating control signals from the microprocessor to an array of solenoid valves associated with the air jets and thereby controlling a flow of air to the air jets.     
     
     
       10. The method of  claim 1 , further comprising:
   conveying the layer of waste paper on a first conveyor and launching the layer of waste paper off the first conveyor across a gap to a second conveyor; and        wherein said controlling step includes controlling said one or more actuators to deflect a portion of the paper away from said second conveyor in an ejected paper stream.     
     
     
       11. The method of  claim 1 , being further characterized as a method of sorting waste paper objects, wherein:
   in said spreading step said one unit thick layer is substantially one paper object thick;        in said detecting step said layer of paper is a layer of paper objects; and        in said controlling step said sheet of paper is a paper object.     
     
     
       12. The method of  claim 1 , wherein:
   the waste paper is provided in a stream including white paper and materials other than white paper; and        the controlling step includes controlling one or more actuators that direct the materials other than white paper out of the stream.     
     
     
       13. The method of  claim 12 , wherein:
   said spreading step includes carrying the stream on a conveyor having a width; and        in the controlling step, said one or more actuators include an array of air jets spaced across the width of the conveyor, and said controlling step includes actuating an appropriate number of said air jets at an appropriate time to direct the materials other than white paper out of the stream.     
     
     
       14. The method of  claim 1 , wherein:
   the waste paper is provided in a stream including white paper and materials other than white paper, wherein the stream is dominated by the materials other than white paper; and        the controlling step includes controlling one or more actuators that direct the white paper out of the stream.     
     
     
       15. The method of  claim 14 , wherein:
   said spreading step includes carrying the stream on a conveyor having a width; and        in the controlling step, said one or more actuators include an array of air jets spaced across the width of the conveyor, and said controlling step includes actuating an appropriate number of said air jets at an appropriate time to direct the white paper out of the stream.     
     
     
       16. A method of sorting waste paper, comprising:
   spreading waste paper out into a layer that is substantially one unit thick;        detecting the presence or absence of a predetermined optical characteristic as the layer of paper is passed by a sensor; and        controlling one or more actuators that direct a paper object based on the presence or absence of the predetermined optical characteristic.     
     
     
       17. A method of sorting waste paper objects, comprising:
   spreading waste paper objects out into a layer that is substantially one waste paper object thick;        detecting the presence or absence of a predetermined optical characteristic as the layer of waste paper objects is passed by a sensor; and        controlling one or more actuators that direct the waste paper object based on the presence or absence of the predetermined optical characteristic.     
     
     
       18. The method of  claim 17 , further comprising:
   providing the waste paper objects in a stream including white paper and materials other than white paper; and        wherein the controlling step includes controlling one or more actuators that direct the materials other than white paper out of the stream.     
     
     
       19. The method of  claim 18 , wherein:
   said spreading step includes carrying the stream on a conveyor having a width; and        in the controlling step, said one or more actuators include an array of air jets spaced across the width of the conveyor, and said controlling step includes actuating an appropriate number of said air jets at an appropriate time to direct the materials other than white paper out of the stream.     
     
     
       20. The method of  claim 17 , further comprising:
   providing the waste paper objects in a stream including white paper and materials other than white paper, wherein the stream is dominated by the materials other than white paper; and        wherein the controlling step includes controlling one or more actuators that direct the white paper out of the stream.     
     
     
       21. The method of  claim 20 , wherein:
   said spreading step includes carrying the stream on a conveyor having a width; and        in the controlling step, said one or more actuators include an array of air jets spaced across the width of the conveyor, and said controlling step includes actuating an appropriate number of said air jets at an appropriate time to direct the white paper out of the stream.     
     
     
       22. A method of sorting waste paper objects, comprising:
   providing a stream of waste paper objects in a layer that is substantially one waste paper object thick;        detecting the presence or absence of a predetermined optical characteristic as the layer of waste paper objects is passed by a sensor; and        controlling one or more actuators that direct the waste paper object based on the presence or absence of the predetermined optical characteristic.     
     
     
       23. The method of  claim 22 , wherein:
   in said controlling step, each of said actuators includes an air jet.     
     
     
       24. The method of  claim 23 , wherein:
   said providing step includes providing said layer on a conveyor having a width; and        in said controlling step, said air jets comprise an array of air jets spaced across the width of the conveyor.     
     
     
       25. The method of  claim 23 , wherein:
   said detecting step includes communicating sensor signals from the sensor to a microprocessor; and        said controlling step comprises communicating control signals from the microprocessor to an array of solenoid valves associated with the air jets and thereby controlling a flow of air to the air jets.     
     
     
       26. The method of  claim 22 , further comprising:
   conveying the layer of waste paper objects on a first conveyor and launching the layer of waste paper objects off the first conveyor across a gap to a second conveyor; and        wherein said controlling step includes controlling said one or more actuators to deflect a portion of the paper objects away from said second conveyor in an ejected paper object stream.     
     
     
       27. The method of  claim 22 , wherein:
   in the providing step the stream includes white paper and materials other than white paper; and        the controlling step includes controlling one or more actuators that direct the materials other than white paper out of the stream.     
     
     
       28. The method of  claim 27 , wherein:
   said providing step includes carrying the stream on a conveyor having a width; and        in the controlling step, said one or more actuators include an array of air jets spaced across the width of the conveyor, and said controlling step includes actuating an appropriate number of said air jets at an appropriate time to direct the materials other than white paper out of the stream.     
     
     
       29. The method of  claim 22 , wherein:
   in the providing step the stream includes white paper and materials other than white paper, and the stream is dominated by the materials other than white paper; and        the controlling step includes controlling one or more actuators that direct the white paper out of the stream.     
     
     
       30. The method of  claim 29 , wherein:
   said providing step includes carrying the stream on a conveyor having a width; and        in the controlling step, said one or more actuators include an array of air jets spaced across the width of the conveyor, and said controlling step includes actuating an appropriate number of said air jets at an appropriate time to direct the white paper out of the stream.