GB931818A - Improvements relating to mills - Google Patents

Abstract

931,818. Ball-and-ring mills. BABCOCK & WILCOX Ltd. May 9, 1962 [May 11, 1961], No. 17317/61. Class 59. [Also in Groups XXIX and XXX] A mill, in which an elastic fluid carries the ground material to a classifier 20 returning oversize particles to the grinding zone for regrinding, has a valve device 32 disposed between the classifier and the grinding zone and consisting of a series of closely-adjacent members 38 pivoted at their upper ends and gravity-biased to overlapping positions to prevent passage of the elastic fluid and movable from these closed positions by the pressure of the oversize particles to effect discharge. As shown in Figs. 3 and 5, inner and outer members 38A, 38B are mounted on a ring 39 which is supported around the lower end of the classifier by webs 33 and a skirt ring 31. Material fed down a central duct 19 is directed, together with rejected material, to the grinding zone between an upper ring 8, which is urged downwardly by hydraulically-operated levers 11, and a lower ring 7 carried by a rotary table 6. Air supplied at 13 is directed upwardly through a throat 17 to carry ground material to the inlet 21 of the classifier. The classifier is provided with pivotable vanes 24 which can be set in the required angular position for whirling the material to cause oversize particles to fall out of suspension but allow suitably ground material to flow through an adjustable outlet 27. The oversize particles fall on to the frustoconical wall 22, Fig. 1, and build up on the bottom wall 36 of the valve device until, under gravity, they push open the members 38 and pass to the grinding zone.