CRUSHING AND PULVERIZING MACHINERY. 



453 



of the hubs has suitable openings through which the material is auto- 

 matically fed by the Gates patent feeder. 



" Resting on the inwardly projecting shelves and reaching from 

 one side plate to the other and bolted thereto are the wearing-plates. 

 These are eccentrically arranged so that one plate passes behind the 

 next one, thus producing a step and also providing an opening through 



FIG. 99. Gates ball mill with feeder attached (Allis-Chalmers Co.), showing grind- 

 ing- plates in position and all other screws removed. 



which residues from the screens are returned to the mill. The tum- 

 bling of balls and material due to revolving the drum rapidly reduces 

 the material to fine grit and powder, the steps serving to greatly in- 

 crease the beating action of the balls against the material. 



"When partially reduced, the ground product falls through aper- 

 tures in the wearing-plates onto the first screen. The rejections from 

 this screen are promptly returned to mill through the openings between 

 the overlapping plates; the screened material falls upon the second 

 screen and the rejections from it are likewise returned to mill, while 

 the fines go to the outside finishing screen, and what passes through 

 falls into the dust-proof housing and is removed by conveyor or other 



