Patent GB-1114314-A (GB)
Title: Improvements in or relating to centrifugal air classifiers
Inventor: MEYER PAUL
IPC: B07B7/083
Filed: 1964-12-11
Abstract: 1,114,314. Centrifugal classifiers. ASSOCIATED PORTLAND CEMENT MANUFACTURERS Ltd. 8 Sept., 1965 [11 Dec., 1964], No. 50647/64. Heading B2P. In an air classifier comprising a casing 20, 22, Fig. 1, in which is mounted a rotor having a top plate 12 and a bottom shroud plate 24 with radial blades 5 extending therebetween, the shroud plate 24 is sloped downwardly towards the centre in order to permit gravity to assist in the rejection of particles at or near "cut" size and not rejected by centrifugal force exceeding the drag exerted by the inwardly flowing carrier air, at least one opening 27 being provided at the bottom of the shroud plate 24 for the discharge of the or near "cut" size particles. The radial blades 5 have slots 14 which allow the material being classified to pass from one compartment between the blades to the next. The material is fed from a hopper 33 via a tube 32 and radial passages 36 into the interior of the rotor. The carrier air is fed via a pipe 31 into an annular passage 34 having a volute-shaped inner wall 37 and passes downwardly through an opening 38 to the outer periphery of the rotor through which it flows radially inwardly. Fine particles are entrained by the air and are removed therewith through a central duct 19 and a volute chamber 35 into a discharge pipe 39. Coarse particles are ejected radially outwardly of the rotor by the greater action of centrifugal force and fall down the cone part 22 of the casing into an outlet 15. The particles at or near the cut point are thrown against the shroud plate 24 and move down it to a central opening which is partly closed by a plate 26. The plate 26 may be spaced from the plate 24 to define an annular slot 27 for the passage of the "cut point" particles under the action of centrifugal force into the interior of the casing part 22 or is joined to the plate 24 and a series of discharge holes are provided. Skirts 40, 40' fixed to the shroud plate 24 prevent air from by-passing the rotor. In a modification, Fig. 3 (not shown) the material is fed into in the rotor interior via openings 47 in the top plate 12. The air and the fine particles discharge downwardly through a curved pipe 41. The particles at or near the "cut point" discharge through a gap 27' between the pipe 41 and the bottom of the shroud plate 24. Air leakages are prevented by vanes 29, 42 and 49. In another embodiment, Figs. 4 and 5 (not shown), the material to be classified is fed together with the carrier air through an inlet 79 opening tangentially into a cylindrical shell 80 which operates as a cyclone. The air escaping upwardly from the shell 80 passes down an annular passage 80' and enters the rotor at its periphery. Particles separated by centrifugal force fall down the inner wall of the shell 80 through an annular slot 86. The majority of particles are swept into the rotor by the inwardly flowing current of air and are classified, whereas a small proportion of heavy particles fall down directly into the reject cone 76. In a modification of the latter embodiment, Figs. 6 and 7 (not shown), the shell 80 has a lower conical section 87 which directs the particles to an annular opening 86 and thence into the classification zone of the rotor through an annular opening 86' in the top plate 63' of the rotor. In a further modification, Figs. 8 and 9 (not shown), the discharge pipe 71 for the carrier air and fines communicates with the upper interior space of the cyclone chamber bounded by the cylindrical shell by means of adjustable hinged valve plates 90, which may be automatically regulated by a device 91, so as to by-pass directly from the cyclone chamber a small amount of the carrier .air and seeper-fine particles entrained thereby as it flows towards the top of the cyclone chamber.