THE EXTRACTION OF THE JUICE BY MILLS 



211 



at a later date in BruUard'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 s\'stem 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 sho\\Ti in Fig. 113. It is to be 

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

 roU, and that a safety valve, h, released the pressure at a predetermined 

 point, no accumulator being employed. 



The introduction of the h3'drauHc 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- 

 cmnulator," shown in section in Fig. 114. 



Fig. 114 



This de\'ice consists of an upright hollow rod, d, which communicates 



with a force pump. This rod also communicates \\'ith the cyhnder, b, which 



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



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



e, it %\iU eventually raise the weights from the flange, and the pressiure 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 



, , „ , , , „ . area rams . , , 



of the rollers, the pressure exerted on the roller is ,. , X weignts 



^ area cylinder 



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



the roller uill lift, and, when once the roller has Hfted, the pressure exerted 



by the bagasse and on the bagasse is constant. 



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



directlv on the back roUer, while ^IcDonald arranged them underneath 



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



