GB946414A - Improvements in wet and dry jigs for classifying particulate material such as, for example, coal and ores - Google Patents

Abstract

946,414. Radiation absorption control systems. MANNESMANN A.G. Feb. 22,1961 [Feb. 26,1960; Oct. 18,1960; Nov. 25, 1960], No. 6441/61. Heading G1A. [Also in Division B2] In a jig for separating materials of different densities, the composition of the material drawn off from the jigging bed is continuously controlled by a control system responsive to the absorption of radiation by a detector associated with a source in a zone of the jigging bed where stratification according to density is complete or nearly complete. In the diagrammatic arrangement, Fig. 1, the composite material 2 is fed over a screen 3 and agitated vertically by compressed air-blasts controlled by valves 4 so that separation by density takes place. A detector 5, which may be a counter, is located within the composite bed and is irradiated by a source of radiation, for example, an isotope of cobalt. The output from the detector 5 varies in accordance with the passage of the radiation through one or the other of the component layers, and may be utilized to control means for altering the rate of draw-off of, for example, the lower layer of the bed through controllable openings 9. A number of detectors 5 may be utilized at spaced positions in the direction of travel of the material, and two vertically spaced detectors may be employed at one or more of the positions, Figs. 3 to 5 (not shown). In a further arrangement, Figs. 6, 7 (not shown), the material on the bed is subjected to air blasts from a blower and is oscillated prior to its examination by a detector subjected to radiation from sources on each side of the bed, and in a modification, Figs. 8, 9 (not shown), or figs. 3, 4 (not shown), a measuring device is added to furnish a continuous indication of one of the components of the mixture. In a further modification, Fig. 10, to prevent loss or incorrect removal of the smaller particles, should the valve 9<SP>1</SP> be held open by a large lump such as that indicated at 16, when there is an excess of the less dense material and the valve 9<SP>1</SP> should be closed. The less dense material causes a signal from the detector 8, and if this signal persists for more than a predetermined interval, the switch 15 is operated to open the valve 9<SP>1</SP> for a short time to allow a large lump such as 16 to be released, if it is impeding the closing of the valve, and the valve to be reclosed after a short interval so that the less dense material is fed over its normal, i.e. upper, path for correct disposal.