Method and apparatus for sorting sheet materials such as banknotes

896,191. Pneumatic separating. PORTALS Ltd., and TOOTH, A. J. March 23, 1959 [Dec. 23, 1957], No. 39975/57. Class 117. In order to separate soiled banknotes and similar sheets which have become progressively soiled and more porous during their use, from a mixture of clean and soiled sheets, the porosity of each sheet is tested and separation effected according to porosity. In Figs. 2 and 3 a suction transfer device 21 carries each sheet from a stack 20 to a gripper bar 22 attached to a hollow drum 23 revolving clockwise. The drum has a porous insert 24 in its periphery, and its shaft 25, 26 are hollow. A vacuum pump is connected to the shaft 25 and a flexible bellows 30 is connected to the drum interior via a tube and shaft 26. Depending on the porosity of the sheet placed over the porous insert the bellows may operate a switch 32 actuating an alarm bell so that that sheet may be manually removed. The other sheets are collected by a roller and conveyer assembly 43 and delivered to a stack 44. Alternatively the switch 32 alters the setting of the assembly 43 so that either the soiled or new sheets are delivered to a separate stack. Instead of an electric switch 32 a pneumatic valve may be used and the soiled sheets rejected by pneumatic controls.