GB790652A - Improvements in or relating to comminuting and classifying apparatus and method therefor - Google Patents

Abstract

790,652. Grinding; pneumatic separating. HARDINGE CO., Inc. June 18, 1955, No. 17685/55. Classes 59 and 117 [Also in Group XXVI] Apparatus for comminuting material comprises classifying means disposed adjacent the exit of a rotary grinding drum 12, Figs. 1 and 2, and consisting of a stationary container 22 for receiving comminuted material from the drum and means 68 for lifting and dispersing such material, so that it may be contacted by a fluid current arranged to entrain, and remove from the dispersed material the finer products of comminution. The drum shown is in the form of a ball mill rotating about a horizontal axis and the container 22 surrounds a peripheral discharge opening in the end part of the mill and engages annular flanges 54, 56 defining the opening; spring-pressed rings 62 seal the joints between the container and flanges. Mounted for rotation with the mill inside the container is a series of radial scoops 68 which are each attached to a block 70 on the flange 54 and arranged to scoop up and disperse the comminuted material discharged from the milling zone into the base of the container; this material passes from the milling zone through apertures in an annular grating 18. The material raised by the rotating scoops is discharged on to the upper face of a hollow truncated cone 74 when the scoops reach their uppermost positions and is deflected thereby through the inner opening in the grating 18 so that it falls as streams into the milling zone; the cone 74 which is carried by brackets 80 from the mill trunnion 58 so as to rotate therewith, is fitted with radial vanes 88 to restrict lateral movement of the material, a screen 84 to prevent the passage of the coarser material and a scoop 86 for returning to the milling zone any coarse material entering the cone. The cone is included in a closed conduit circuit 24, 28, 36, 40 including an initial separator 26, collector 30 and fan 38 which provides suction through the conduits 24, 28 and discharges an air stream through the conduit 40 axially of the mill and container. The axial air stream, 'which is regulated by dampers 44, 94 passes inwardly to the container where it is effective, as shown by the arrows 96, to entrain fine material dispersed by the scoops 68 for removal through the suction conduit 24. The main air stream, after passing through the cone 74, circulates as shown by the arrows in Fig. 1 in the mill and is withdrawn together with the fine particles of comminution through the openings in the grate 18 and suction conduit 24; as it enters the milling zone this stream impinges upon the downward stream of material deflected by the cone 74 and in addition to taking up the lighter particles therefrom, urges the coarser particles towards the inlet end of the mill. To vary the proportion of the air stream which enters the milling zone, a sleeve 100 is adjustable axially to and from the cone 74 by a level 102. In the modification shown in Fig. 6, the air current instead of being intoduced axially is fed by a fan 120 through a main conduit 122 controlled by dampers 126, 128 and two branch conduits 130, 132 transversely into the container 22. A damper 134 determines what proportion of the air stream passes through the conduit 132 and the current from this conduit acts upon the comminuted material picked up by the scoops to remove the finer products through the suction conduit 24; the coarse products are deflected by the cone 74 back into the mill. An air current is also passed axially through the mill from the inlet end.