GB979925A - Multi-purpose mill - Google Patents

Abstract

979,925. Impact pulverizers. H. A. MERGES. June 6, 1962 [June 9, 1961 ; April 13, 1962], No. 21887/62. Heading B2A. A mill for disintegrating, sifting and separating materials comprises a tapered grinding ring 6, Fig. 1, the largest diameter of which faces the side at which the grinding stock is centrally fed into the mill, a rotor 4 arranged within the ring and having beating elements 5 shaped to match the grinding face of the ring, a classifying chamber 9 defined by the rotor 4 and a screen 7 and the inner edges 8 of the beating elements, and an annular slot 25 provided in front of the largest diameter of the grinding ring and communicating with an annular chamber 10, the cross-section of the slot being variable by a screen. The material is fed to the machine through a hopper 3 to a chamber 13 where it is ground in a zone 18 by the beating elements 5 and the ring 6. The coarser material, such as husks and shells of kernels in the case of cereals, tends to flow towards the largest diameter part of the ring and if the slot 25 is open, it is discharged through chamber 10. If the slot is closed by axial movement of the screen 11, the coarse material is crushed to a degree permitting it to be moved by the air flow in the mill. The elements are mounted on the rotor at a slight angle and the rotor is axially displaceable to vary the distance between the elements and ring. The radial distance between the ring 6 and outer edge of the elements is less than the radial distance between the outer edges of the elements and the circumference of the rotor. A grid 17, Figs. 1 and 2, is secured to the screen 7 and directs the finely crushed material in the classifying chamber 9 through an aperture 19 into a discharge channel 14 ; any coarse particles in chamber 9 are forced by the spiral air flow in the chamber back into the grinding zone. In another embodiment, the rotor 4 has pins extending into the chamber 13. The beating elements need not extend from the rotor towards the input side of the mill and a flange may be mounted on the circumference of the rotor to permit the grinding zone to be adjusted. In a further embodiment, the face of the grinding ring is provided with axially-extending grooves. In yet another embodiment, the grid 17 is formed as a vane-type wheel rotatable independently of the rotor to pass finely crushed material to the discharge shoot and to return coarse material to the grinding zone.