GB1346566A - - Google Patents

Abstract

1346566 Radiation sorting apparatus COAL INDUSTRY (PATENTS) Ltd 19 April 1971 [14 Nov 1969] 55929/69 Heading G1A Objects are sized before passing through a beam of radiation, and the radiation intensity or detector output adjusted in accordance with the sensed size. In sorting apparatus, this adjustment is to avoid mis-sorting of wanted material due to e.g. an extra large piece of wanted material affecting the radiation to an equal extent as does a much smaller piece of unwanted material. In the described embodiment, coal is sorted from rock by an X-ray absorption gauge having source 5 directing via collimators fourteen beams towards an array of fourteen photo-multipliers 6. Each controls via delay circuit 9, a mechanical finger, 7, 8. The sizing device in this case is a sensing finger 13 having a nylon tip which rides over the pieces A, B under spring pressure and via coupling arrangement 15, 16 (a Bowden cable) adjusts the position of filter wedge 17 in a collimator slit. Alternative adjustment means. Many other ways of attenuating the radiation beam are referred to, which may be in the radiation path before or after the test object. This may be absorbing or reflecting means e.g. a filter, ridge, comb shaped device or iris diaphragm. Alternatively the source output (by lamp voltage control) or detector signal may be affected. Alternative Radiation path configurations. Any form of electromagnetic radiation besides X-rays may be used e.g. visible or U.V. radiation. Ionizing particle radiation is also envisaged. Instead of absorption measurement, fluorescence measurements or reflection measurements may be made. The detector may be located to receive radiation emitted at right angles to the incident beam. The bodies may be tested as they drop through a radiation beam, when air blast rejection is used.