THE EXTRACTION OF THE JUICE BY MILLS 



221 



A steep vertical angle, then, while calling for a narrow trash turner, 

 and decreasing the intensity of the side thrust, calls for an increased intensity 

 of the hydraulic pressure to maintain the same pressure on the bagasse 

 as is obtained with a flatter vertical angle. 



The magnitude of the resultant AN or R and of the horizontal component 

 H can be obtained in terms of V, the hydraulic pressure, thus : — 



(AN)^ = {AMy- + {Aiy = (p {n -i)^/- 



But 



+ 



' 2 / 



= P^ (^^ + I + 2 n cos a) 

 V2V 



p{n-\- l)^^ 



I + cos a 



AN = Rsindp = 



{n -\-i) V I + cos a 



, „ \/2 F V ^^""^ + I + 2 W cos a 



whence R= = — 



(W + l) V I + cos a 



Also {A M)2 = {A Ny -{A L^, where A M = H, A N = R, and 

 whence 



2 F^ (w2-[- I -f 2 W cos a) 



AL = V; 



H2=- 



(w + l2(l +COS a) 



F2 



n^ — 2w-{-i — cos a {n^ — 2n-\-i) 



(w+l)" (l+COS a) 

 (W — l)2 — COSa (n — 1)2 



72 



or 



{n- 



■l)2(l-fC0S a) 



72 



■i)VT 



■cos a 



(«+l) Vl + COSa 



Finally, the resultant R makes an angle, /?, with the horizontal such that 



o V w-j-iVi+cosa 



n. n~TVl — COS a 



The Actual Pressure on the Rollers. — In a 



mill controlled b}' hydraulic pressure, the actual 

 pressure exerted on the rollers by the bagasse 

 in its passage is, of course, controlled by the 

 hydraulic load and b}- the vertical angle. A 

 graphic representation of this pressure can be 

 obtained as follows: — 



In Fig. 127 let ace represent a miU roller 

 to which a tangent is drawn at c. From a draw 

 ah perpendicular to this tangent : then denoting 



he by /, ah by d and oa hy t , d = r — v r 



If the lower circle represent a second 



roller separated by a distance k {k is 



then 



mill 

 the 



opening 



H = k + 2 {r — Vr 



l^ 



where H is the distance between the rollers at 



any length /, measured from a point on either 



circle obtained b}' joining the centres of the 



circles ; that is to say, along the tangent from Fig. 127 



the point of nearest approach. 



On page 189 is given a table sho\\ing the volume (or height of a column) 

 of bagasse under known pressures. The quantity of bagasse used in this 



