GB817341A - Improvements relating to grinding mills - Google Patents

Abstract

817,341. Ball mills. MITCHELL ENGINEERING Ltd; April 20, 1956 [Jan. 21, 1955], No. 1937/55. Class 59 [Also in Group XXVI] A ball-tube type of grinding mill comprises fixed feed and discharge boxes 24, 25 for introducing air or other gas and material to be pulverized into the mill and for discharging pulverized material from the mill, and sealing rings 31, each including a labyrinth seal, adjacent to the clearances between the fixed and rotating parts of the mill, means being provided for supplying air or other gas to the sealing rings to pass through the clearances into the mill to prevent egress of pulverized material through the clearances. The drum 1 has secured thereto head castings 4 each comprising a frusto-conical wall 5 supported by spokes 6 from a boss 7. The boxes 24, 25 each comprise a cylindrical part 26 fitting, with sufficient clearance to allow rotation of the mill, within a bore 27 formed in the frusto-conical wall 5. Each sealing ring 31, which is formed in two semi-circular halves, Fig. 5, which are clamped on to the cylindrical part 26 by means of bolts 30, encloses an annular chamber 32 to which air or other gas is supplied through a conduit 34. The end face of each frusto-conical wall 5 is formed with grooves 35 into which fit projections 36 formed on the sealing ring to form a labyrinth seal. To allow for thermal elongation of the drum 1 during operation, the projections 36 at the discharge end of the mill, Fig. 3, extend only partly towards the bottoms of the grooves 35 when the mill is cold. The bottom of each chamber 32 is provided with a pipe 40 leading to a trap 41 for material which may have entered the seal from the grinding chamber. Material is fed to the box 24 from a source 21, Fig. 1, by means of a motor-driven table feeder 16. The cylindrical shell 14 of the mill has bolted thereto, with the interposition of cork or like insulation, corrugated liners 15. Replaceable liners 17, 18 also, if desired, with the interposition of cork or like insulation, are provided on the frustoconical walls 5, and similar liners 22, 23 are provided on the inner faces of the bosses 7 and spokes 6. Specifications 594,855 and 672,588 are referred to.