GB601608A - Improvements in fine reduction mills and method of fine reduction - Google Patents

Abstract

601,608. Grinding-mills. CROSS, E. J. (Nordberg Manufacturing Co.). May 31, 1945, No. 13694. [Class 59] A method of grinding materials includes the following steps: maintaining in a grinding zone superjacent to a gyratory impacting member a mixed mass comprising particles of material to be ground and separate loose impacting elements; gyrating the said impacting member at a sufficient speed and with sufficient amplitude of movement to throw a substantial proportion of the mixed mass upwardly and clear of the impacting member, through a distance sufficient to ensure an ensuing free fall of the upwardly projected mass; and thereafter catching the falling mass upon an upwardly moving part of said impacting member so that the ensuing impact enhances the crushing action of the loose impact elements in the falling mass, the impactive action progressing sequentially around the grinding zone and the inertia of that proportion of the mixed mass which is impacted by the gyratory impacting member at any given instant being substantially less than the inertia of said impacting member. A shaft 15, driven from a shaft 6, Fig. 2, by gearing 17, 16 is mounted in bearings 14, 21 in a housing sleeve 9, 10, 11 mounted between I beams 1. A spherical bearing element 23 mounted on the upper end of the sleeve 9 engages a concave spherical element 42 to support the mill proper, which comprises a housing 30, 33, with lining 70, 76, 78, having a sleeve part 34 fastened at its upper end to a sleeve 40 carrying the element 42. The sleeve 34 is secured at its lower end to a member 68 having a sleeve 62 in bearings 61 of which an eccentric arm 18, which forms part of the shaft 15, engages, so that, as the shaft 15 rotates, the member 68 and thus the mill is given the required gyratory movement. To prevent bodily rotation of the mill housing it is flexibly connected by compression bolts 93, Fig. 2, spacers 94 and rubber masses 96, 98 to an I beam. Material from a feed spout 51 falls onto a cover member 50 on the sleeve 40 and drops through an aperture 32 into the mill housing. The action of the mill moves the fines toward an outlet 72 around the sleeve 34 and into an outlet chute 75. The grinding bodies may be balls or rings surrounding the centre sleeve. The amplitude and speed of the gyration are so related as to obtain the best impacting effect, which occurs when the falling mass hits the bottom impacting plate of the mill when said plate is moving upwardly at its maximum velocity. Lubrication oil passes from the interior of the sleeve 40 through channels 43 in the member 42, over the spherical surface 23, through channels 46 and over the shaft bearings 21, 14 down to a gear pump 101 and is then pumped back to the sleeve 40 through a pipe 100. The mill may be used for wet grinding. In a modification described the gyrating bowl is positioned below the driving shaft 6.