GB689936A - Improvements in or relating to sieveless centrifugal mills - Google Patents

Abstract

689,936. Impact pulverizers. ALPINE AKT.-GES Feb. 19, 1951 [April 22, 1950], No. 3958/51. Class 59 In a centrifugal mill, preferably of the peg type, having two discs 1, 2 rapidly rotating at different speeds in the same or different directions, the slower disc 2 and its driving motor are mounted on a hinged access door 19 and the surrounding chamber 5 is of large diameter so that the ground material, having lost its energy before it strikes the outer wall, adheres only loosely to the chamber walls. The motor is mounted on a pivoted frame to facilitate belt - tensioning, particularly when the pulley sizes are altered. Formulae are given for the chamber diameter required at different rotor speeds. For controlling the temperature in the grinding zone and for varying the fineness of grinding, the amount of air or other gas entering the grinding zone is controlled by a valve 8 or by a flap or exchangeable nozzles in the feed pipe 3 and the feed device 7 is made air-tight. Air or other gas, for cooling, drying or chemically treating the ground material, is introduced through valves 9 and blower vanes 10 on the discs direct it into the chamber 5, the edges 12 of the discs and the walls of the chamber being formed so that the streams of ground material and gas are prevented from directly striking the chamber sides; alternatively, the air or gas may be intro'- duced tangentially into the sides of the chamber outside the grinding zone. In the modification shown in Fig 2, the inner surface of the faster disc 1 is flush with one wall of the chamber and ground material is deflected into the chamber by the stream of gas, the deflection preferably being assisted by a shroud 13 on the disc 1. The speed of the discs may be sufficiently high to induce supersonic vibrations in the stream of gas passing through the grinding zone.