The Phosphates of America. 121 



of a steel ring, against which they exert a pressure of some 2000 

 pounds per square inch. The effect of this force is augmented by 

 a differential grinding motion imparted by the drivers. 



As fast as it is produced, the pulverized is separated from the 

 coarse material, by gravity, being drawn from the mill through 

 pipes connected with the top of the casing by an exhaust-fan, and 

 carried to settling bins or chambers. 



Five different varieties of steel, each having special character- 

 istics suited to the requirement, are used for the interior or work- 

 ing parts of the machine. The wearing parts, being few in number 

 and simple in shape, are readily replaced when worn. 



The construction of the mill will be easily understood from the 

 following transverse vertical section through its centre. 



The shaft S is of hammered steel, 39 inches between bearings, 



THE FRISBEE-LUCOP PHOSPHATE MILL. 



which are 3j inches by 10 inches long. Pulleys are double-arm,, 

 fast and loose, 28 inches in diameter by 8-inch face. 



To the shaft is keyed the driving-arm A A previously forced 

 on. This is a solid casting 6 T 1 ^ inches thick through the ends and 

 9-J inches through the flanges or hub. The rear ends of the arm 

 are made concave to receive the rolls when the mill is at rest. 

 Upon both sides of the arm are fastened the discs D D ? annular 

 plates fitting around the flanges of the arm and firmly secured to 

 it by two disc-bolts If inches in diameter. 



Between the discs are placed the drivers B B, two in number, 

 rigidly bolted to the discs by the two driver-bolts, 1^ inches square. 

 The drivers are cylindrical, 6 T ^ inches long by 6 inches diameter, 

 made of cast-steel or forged iron, and weigh 45 pounds each. When 

 worn by contact with the rolls they may be turned a quarter cir- 

 cumference on the bolt. This may be repeated until the four 

 sides are worn. 



