A Noncontact Sensor for the Identification of Paper and Board Samples on a High Speed Sorting Conveyor

Sorting of recovered paper into cardboard and paper based on visual imaging alone can be misleading and a bending stiffness based sorting process will be more effective in identifying cardboard from thin paper grades. In this paper, a relative bending stiffness sensing technique for discrete high speed moving samples is presented. The sensor estimates the bending stiffness of the sample by measuring the deflection of paper when subjected to a transverse pneumatic pressure load exerted by a carefully selected and positioned nozzle. Results from laboratory static deflection measurements, and dynamic tests on a pilot plant conveyor show that the sensing concept is capable of identifying mixed waste into three broad categories, namely, light weight paper, medium weight cardstock, and heavy cardboard, with certainty.