266 ANNUAL REPORT 
The oversize comes back at the rate of 200 tons per hour, making the 
amount handled 500 tons per hour. The fine rolls crush the 14-mesh mate- 
rial and reduce it to 1-50 of an inch screen at the rate of 135 tons per hour, 
to which is added the oversize which is returned to the rolls. 
Each set of these mills requires power as follows, No. 6 being the 
coarser and No, 7 the finer rolls: | 
| 
| 
When empty, Crushing 
horsepower. horsepower. 
No. 6 rolls... 10 260 
NOveorollsin2 eae eae. 3 seen cares IQ: 150 
Edison thus does both the intermediate and fine grinding with rolls. 
Disintegrators. —These are true impact crushers and consist essen- 
tially of several cages of round bars revolving in opposite directions. 
The material is ted at the center, 1s) struck by the bars ol the imuer 
cage and partly broken and takes a direction tangential to this cage, 
when it is struck by the bars of the second cage, revolving rapidly in 
the opposite direction. This type of machine is represented by the Sted- 
man mill and other later makes. By means of a bar projecting into 
the inner mill, lumps or cakes forming on the inside are broken up. 
The machines vary in size from 30 to 50 inches, and the bars are from 
I to 134 inches in diameter, according to the size of the machine. This 
machine is well suited for handling almost dry clays, soft shales and 
coal, for which materials it has a great capacity and is very efficient. It 
is not so well adapted to heavy grinding. A 40-inch machine will 
erind 175 to 200; a 50-inch, 350 to 400; a 60-inch, 500 tons of 
coal per day, requiring 35 to 50, 70 to 100, 100 to 125 horsepower. A 
36-inch mill will grind from 90,000 to 140,000 pounds of clay per day, 
requiring 12 to 15 horsepower; a 40-inch mill will prepare 150,000 to 
200,000 pounds of clay, requiring 15 to 20 horsepower. 
For heavier work the pulverizers of the hinged hammer type are 
employed (see figure 38,) and have in a number of cases proven quite 
successful. In one plant the crushings from the rock breaker 114 inches 
im size “are “taken Gand sreduced) soy thal SA) pemiacemtpaccesmea 
20-mesh sieve, by a Williams pulverizer, showing a capacity of 137 tons 
in If hours, with a consumption of about 75 horsepower. The material 
is a mixture of limestone and shale. These machines, unlike the Sted- 
man type, do not consist of several cages, but simply of hinged hammers 
