ES342181A1 - Rotary grinding mill - Google Patents

Abstract

A ball or tube mill containing loose grinding bodies includes a built-in dam ring 3, Fig. 1, constituting a partition between a grinding chamber 1 and a discharge chamber 2 that has an outlet for the ground material. The discharge chamber has means to return the grinding bodies to the grinding chamber through the dam ring. The discharge chamber has lifters 7 for the grinding bodies adjacent the outlet side of the dam ring, and the grinding bodies in falling off these lifters tend to pass back through the opening 8 in the ring 3. The dam ring may be provided with openings, and scoops 11 to lift the ground material and discharge it into a hollow trunnion 5. In a further embodiment, the opening in the dam ring may be surrounded by a frusto-conical ring and the chamber 2 may have a frustoconical lining and a suspended plate which with a screw-thread in the trunnion further assists return of the grinding bodies to the mill. Other embodiments include a triangular section ring around the opening in the dam ring 3, and a plate carrying a frusto-conical protrusion a mill with three discharge compartments and a conveyor screw in the trunnion a mill with three compartments with dam rings 3', 22', 23', Fig. 7, whose central openings successively increase in diameter and a mill in which the last chamber has a lining so that there is a reduction in internal peripheral speed of the chamber and hence in the consequent tendency for grinding bodies to leave the chamber at its outlet. In a further embodiment two spiral rings 29, 30, Fig. 10, each have a mouth 31, Fig. 9, at the periphery of the discharge chamber 2. As the mill rotates some grinding bodies pass through the mouth 31 and move along the tube to its curved end 32 and are thus returned to the preceding grinding chamber. Ground material passes over a frusto-conical lining 14, through openings 9 in a dam ring 4, to be picked up by scoops and delivered into an outlet trunnion 5.