GB1195601A - Mineral Sorting Apparatus - Google Patents

Abstract

1,195,601. Sorting, measuring physical properties electrically. INTERNATIONAL SORTING SYSTEMS CORP. Jan. 9, 1968 No. 1271/68. Heading G1N. [Also in Division B2] In apparatus for sorting pieces of mineral according to a given characteristic, such as metal content, the pieces are introduced to the centre of a rotating table 28 having a plurality of channels 29 arranged around its edge through which the pieces are urged by centrifugal force. At the outer end of each channel is a sensor 37 and a sorting flap 33 which is operated to deflect a piece into an inner chamber 27 if the sensor 37 detects the given characteristic in the piece. The pieces are otherwise received in an outer annular chamber 26. A rotatably mounted inertia plate 22 has downwardly projecting plates 23, 24 for crushing any oversize pieces. As shown in Fig. 6, the sensor 37 comprises a coil 36 in the tuning circuit of an oscillator 43 arranged so that passage of piece of mineral having a high metal content near the coil 36 changes the frequency of the oscillator. A second oscillator 45 provides a reference frequency which is mixed with the output of the sensing oscillator to produce constant amplitude pulses 48 at the beat frequency. Normally, that is in the absence of a piece of mineral of high metal content, the potential at point 49 is such as to hold transistor Q2 about half way between cut-off and saturation, and transistor Q3 short-circuits the sorting flap operating means 35. The frequency of the reference oscillator 45 is controlled by a voltage fed to a diode D3, Fig. 7 (not shown), having a voltage dependent capacitance connected in parallel with coil 44 in the tuning circuit of the oscillator 45 to compensate for long term drift. On detection of a piece of mineral having a high metal content, the beat frequency increases thereby raising the voltage at point 49 to saturate transistor Q2 and block transistor Q3, thus allowing the sorting flap 33 to be operated.