THE EXTRACTION OF THE JUICE BY MILLS 



211 



at a later date in Brullard's U.S. patent (422289 of 1890), shown in 

 Fig. 112. The writer knows of a mill operating over a whole crop with a 

 makeshift arrangement similar to this, on the occasion of a locally irrepar- 

 able accident to the hydraulic system. 



Hydraulic pressure, the system adopted in nearly all plants of recent 

 date, was first suggested by Jeremiah Howard (U.S. patent 21340 of 1858). 

 His design, of very considerable interest, is shown in Fig. 113. It is to be 

 observed that the pressure was obtained by a pump, a, driven off a mill 

 roll, and that a safety valve, b, released the pressure at a predetermined 

 point, no accumulator being employed. 



The introduction of the hydraulic really dates from Stewart's patent 

 (3269 of 1871) and from McDonald's patent (U.S. 128235 of 1872). As 

 designed in both these inventions, the pressure is obtained from an " ac- 

 cumulator/' shown in section in Fig. 114. 



FIG. 114 



This device consists of an upright hollow rod, d, which communicates 

 with a force pump. This rod also communicates with the cylinder, b, which 

 supports a number of removable weights, c, on the flange, k. When oil 

 or other fluid is pumped into the cylinder from the pump, a, through the pipe, 

 e, it will eventually raise the weights from the flange, and the pressure in 

 the system will be that due to the weights. If the pipe e is continued 

 so as to communicate the pressure to rams bearing on the brasses 



of the rollers, the pressure exerted on the roller is 



area rams 



X weights 



area cylinder 



supported. When the bagasse in its passage exerts a pressure equal to this, 

 the roller will lift, and, when once the roller has lifted, the pressure exerted 

 by the bagasse and on the bagasse is constant. 



The location of the rams varies. Stewart placed them preferably acting 

 directly on the back roller, while McDonald arranged them underneath 

 the mill and operating on the top cap through the king bolts, as shown in 



