448 CEMENTS, LIMES, AND PLASTERS. 



Kominuter. The Lindhard kominuter, like the ball mill, is a drum- 

 shaped device, about as high as broad, suspended by a shaft passing 

 through the heads and resting on bearings. Outside of this drum 

 is a coarse perforated cylindrical plate, and this in turn is surrounded 

 by a screen frame fitted with wire screening cloth. The material is fed 

 to the kominuter, as in the ball mill, through an opening near the shaft 

 at the head end of the mill. It passes from this to the other end, being 

 ground meanwhile by the balls, because its only place of exit is at the 

 tail end of the kominuter. The discharge material passing thus out 

 of the inner drum, returns in opposite direction over the perforated 

 plates, the coarser particles being returned to the inner drum by curved 

 pipes. Of the material which succeeds in passing the perforated plate 

 the finer particles go also through the final exterior screen and are sent 

 to the tube mills. The coarser particles, rejected by the exterior screen, 

 are returned to the inner drum by two other curved pipes. 



This arrangement, while giving a regular and fine product, prevents 

 excessive wear on the wire-cloth screens, since most of the coarser par- 

 ticles do not reach them, being rejected by the perforated plate. 



The kominuter was designed to overcome certain disadvantages 

 which have become apparent in machines of the ball-mill type. As 

 stated by the manufacturers of the kominuter, the ball mill had the 

 following defects : 



I. Insufficient screen area to prevent materials already ground fine 

 enough from returning to the mill to be acted on again. 



II. The gradual closing of the holes in the perforated grinding 

 plates under the peening action of the balls, resulting in a daily de- 

 crease in the output from the ball mill. 



III. The impracticability of lining the drum with the multiples of 

 a single templet small enough to be handled by one man; that is, the 

 lining is either a set of plates few of which are to the same templet or 

 else a single plate to each face of the polygon, made so large as to re- 

 quire much power to handle. 



IV. The lack of means of easy adjustment to allow for the widely 

 varying grind ability of materials, as well as for the desired fineness. 



The manufacturers present the following comparative statement, 

 designed to show the manner in which these defects have been overcome 

 by the kominuter. 



