THE EXTRACTION OF JUICE BY MILLS. 



In Fig 126 let a, 3, and c represent the centres of the rollers of a three- 

 roller mill ; let the angle lac be, as is very usual, 84 ; then the angles abc 

 and acb are each 48 ; let w represent a vertical pressure applied to the top 

 roll ; the line along which w acts will if produced bisect the vertical angle of 

 the mill, so that the angle cad is 42 ; the component of w along ac, that is 

 along the line joining the centres of the top and back roller, is W cos 2, so 

 that if w is 300 tons, the pressure on the megass is 300 X 743 or 222-9 tons. 

 If now a horizontal pressure w 1 be applied to the back roller, the component 



FIG. 127. 



along ac is w 1 cos Ij.8 and if w 1 be 300 tons, this quantity is 300x*669 or 

 200-7 tons; hence with mills of the usual pattern a greater effective pressure 

 is obtained when the hydraulic acts on the top roller. 



The above argument shows too how with a small apex to the mill a greater 

 effective pressure along the line joining the centres of the top and a lower 

 roller is obtained ; neglecting the difference in opening between top and front 

 and top and back roller, this is given by w cos a 2 where w is the vertical 

 pressure on the top roller and a is the apex or verticle angle of the mill. 



197 



