GB183134A - A process of obtaining powders of great fineness and apparatus therefor - Google Patents

Abstract

183,134. Podszus, E. July 12, 1921, [Convention date] Impact pulverizers.-In a process for finely disintegrating and powdering materials, especially metals, the particles of material which are to be reduced are suspended in gas, air, or other fluid medium which is caused to circulate continuously in the form of two opposed aligned streams from the opposite sides of a suitable casing, the constant pounding of the particles against one another caused by the great velocity of the circulating system producing the pulverization of the particles. The particles flow with the currents in a rectilinear as well as in a relatively lateral direction, so as to produce friction upon the impinging of the particles. The apparatus shown comprises a casing 1 containing air propellers or the like 4, 5 mounted on shafts 2, 3 which are rapidly driven in opposite directions by means of pulleys 9, 10. Transverse beaters 6, 7 are provided in front of the propellers and the material to be comminuted is introduced through an opening 8. The propellers produce air currents which impinge upon each other at the central part of the casing, and the beaters produce lateral displacements of the air currents. Lateral cavities are provided in the casing 1 at the rear of the propellers to ensure the air circulation. The bearings of the shafts 2, 3 are cooled by means of water &c. circulating in cavities 15, 16. Preferably about twothirds of the casing is filled with air or liquid, and the remaining one-third with the material to be comminuted. The air or other fluid is introduced into the mill through the conduits 17, 18 from the main conduit 19 so as to create a certain over pressure therein, to cause the finer particles to be discharged into the container 21 when the slide 20 is open. An air conduit 22 with a tangential nozzle enters the container 21. The finer particles ascend the container, which has a restricted portion 23 and an upper funnelshaped portion 24, and the coarser particles fall into the inner funnel 25 and may be returned to the casing 1. The air current passes into separating-devices 26, containing sieves or the like 27, and may be returned by a pipe 28 to the mill. In order to obtain the very finest subdivision, even to colloidal fineness, particles already very fine are mixed with a large number of coarser particles, for example small balls, and caused to a.ct upon one another within the circulating system. The balls or coarse particles employed are of the same material as that to be disintegrated.