LIME Al^B CEMENT INDUSTEIES 



715 



Residrue to the linear inch, of sieve-holes 



I 





180 

 per 

 cent 



100 

 per 

 cent 



38 



76 

 per 

 cent 



50 

 per 

 cent 



OUTPUT 



1 Material entering mill 



47 



34 



28 



2f tons an hour 



Material leaving 



23 



73 



12 

 67 



6 

 63 



1 

 56 







3 Material entering 



4i tons an hour 



Material leaving 



37 



24 



16 



6 



At many works the ball mills and tube mills are used in con- 

 nection with each other. 



Griffin mill (pi. 22). The GrifSn mill is used at some factories 

 for grinding the finished product. It consists of a steel ring, 

 against the inside surface of which a heavy steel roll revolv- 

 ing on a vertical shaft presses by centrifugal force. The mill 

 is j)rovided with screens, so that, as soon as the material has 

 reached the required fineness, it can pass through, the coarser 

 particles however dropping back into the mill. This type is much 

 used in German and other continental works. 



The Grifiin mill is used chiefly for grinding those particles 

 which have been rejected by the sieves, and often in conjunction, 

 with millstones. In many factories however it performs the en- 

 tire work of reduction. The crushing roll is attached to a shaft 

 suspended vertically from a ball joint. To the bottom of the roll 

 there is attached a series of plows or stirrers, so that, when the 

 pan below contains sufiicient material to come in contact with. 

 the plows, it is thrown, up between the crushing roll and the die. 



Two sizes of this machine are made, the diameter of the ring 

 or die of the smaller being 30 inches and of the larger 36 inches^ 

 the diameters of the respective rolls being 18 and 22 inches* 

 The pulley speed for each machine is 200 and 150 revolutions a 

 minute. 



Butler states that, at one mill where two of these machines are 



