EIME AND CEMENT INDUSTRIES 

 Residue to the linear inch of sieve-holes 



715 





180 

 per 

 cent 



100 

 per 

 cent 



38 



76 

 per 

 cent 



50 

 per 

 cent 



OUTPUT 



1 Material entering mill 



47 



34 



28 



2£ tons an hour 



Material leaving 



23 



72 



12 



67 



6 

 62 



1 

 56 







2 Material entering 



4£ 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 Griffin 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 provided 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 Griffin 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 sufficient 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 



