GB1305192A - - Google Patents

Abstract

1305192 Sorting objects photo-electrically UNITED KINGDOM ATOMIC ENERGY AUTHORITY 30 April 1970 [19 May 1969] 25529/69 Heading G1A [Also in Division G2] Translucent bodies are sorted from opaque bodies by passing the bodies 5 in sequence through a radiation beam 2' having one dimension small in relation to the body size and detecting radiation emitted from those parts of the body which are not directly illuminated. If the body is opaque, radiation will be scattered from the body only at the point of incidence Fig. 1a (not shown), and thus will not be detected, but if the body is translucent some penetration and internal reflection will occur Fig. 1b (not shown), and radiation will leave the body from an area around the irradiated one to impinge upon the detector. This method may be used in the extraction of low-grade uranium to differentiate between translucent fragments of quartzite containing 30 Á gm uraninite and opaque fragments containing 400 Á gm uraninite. The light source may be a laser, tungsten iodide lamp, quartz iodine lamp or a xenon arc, and a narrow beam is produced using a slit 9. An occulting bar 8' is provided in the direct light path between the irradiated part of the moving fragment 5 and a photo-multiplier or silicon photo-diode 6'. If the fragments are sufficiently large a plurality of illuminated areas may be provided. In another embodiment - Fig. 4- light is directed towards a moving sample along a fibre optic light guide 11. Any directly reflected light from an opaque fragment is received back on the surface 13 of this bundle, but light scattered back from a translucent fragment is received on a surface 14 of a bundle 12 and is transmitted to a detector 16. In other embodiments Figs. 6, 13 (not shown) the transmitting surface 13 comprises in X-section a plurality of parallel strips (13') alternating with parallel receiving strips (14'). Alternatively Fig. 7 (not shown) the transmitting surface may be in the form of a cross (13") bounded by receiving surfaces (14"). The physical sorting is effected by allowing the fragments to fall in sequence past a detecting arrangement of the kind previously described. The detector output is fed to a threshold device which, after a suitable time delay, operates a mechanism for rejecting unwanted fragments in to a different hopper from the one that receives opaque fragments Fig. 14 (not shown).