Patent GB-1493273-A (GB)
Title: Sorting apparatus
IPC: B07C5/34
Filed: 1975-07-04
Abstract: 1493273 Photo-electric scanning SPHERE INVESTMENTS Ltd 4 July 1975 [4 July 1974] 28213/75 Heading G1A [Also in Division G3] In apparatus for sorting particles of ore 11, moving in a wide random stream, signals from light detecting means 22 scanning across the stream are analyzed with respect to imaginary channels defined by electronic means and which overlap each other across the stream as shown diagramatically by A 1 , A 2 , A 3  etc., circuit and control means being provided for each channel to accumulate data on the particles of ore therein and in dependence on this to actuate two or more air blast channels B 1 , B 2 , B 3  etc. of deflection means 23 extending across the stream. In one embodiment, Fig. 3 (not shown) a pulse train from an oscillator (37) controlled by a belt speed sensor (36) controls the scanning device 22 and a signal discriminator (42) receives the output of the scanning device and provides one output signal related to the size of a particle and another related to the characteristics of the reflected light. The pulse train is also fed to a decade counter (50) and a forty stage shift register (46). The counter is connected to a decoder selector (51) which on one output provides start/stop pulse trains for an analyzing channel circuit (60) and on another output start/stop pulse trains for a gating channel circuit (64). The shift register (46) provides enabling signals for each blast channel in turn in synchronism with the progress of the scan across the stream. In a circuit module (56) for each channel, the circuit (60) passes the light characteristic signal to an arithmetic unit (61) when enabled by the decoder selector (51) and the shift register. The arithmetic unit compares the light signal according to a predetermined programme and if necessary passes an enabling signal to AND gate (62). The gating channel circuit (64) is enabled by the shift register (46) and decoder selector (51) to provide gating channels D 1 , D 2 , D 3 , etc. which prevent analysis of ore particles which just extend into an analyzing channel. A control circuit (65) receives the area signal from the discriminator (42) and when enabled by the gating channel circuit (64) passes one pulse per scan for every scan on which a particle is present to a 16 stage shift register (66) which is thus loaded according to the length of the particle. Another output from control (65) inhibits AND gate (62) while a particle is present and enables it on the first scan which is clear of a particle. If the arithmetic unit (61) is also providing an enabling signal the AND gate passes a decision control signal from a gate (63) to a second 16 stage shift register (67) which then receives the stored information from the first 16 stage register (66). A timer (55) with inputs from the oscillator (37) and 40 stage register (46) provides an air blast timing signal to the second 16 stage register (67) and shifts the number stored therein to OR gates (70, 71) which operate air valve controls (74, 75) via delay means (72, 73). A second embodiment is described Fig. 7 (not shown) in which an additional set of circuit modules provide overlapping channels lying parallel to the direction of scan. The circuitry then calls for decisions at a predetermined number of scans as well as when a particle leaves the scanning zone.