THE EXTRACTION OF THE JUICE BY MILLS 231 



essential part of the train of mills. Their object is not so much to extract 

 juice as to prepare the matted mass of cane for subsequent milling, presenting 

 an even, level, disintegrated blanket to the first mill of the train. Their 

 introduction into Cuba was based on increase in capacity afforded to existing 

 plants rather than on any increase in the quantity of juice extracted. It is 

 for the same reason that the double and even the triple crusher has been 

 very lately introduced into that island. 



The hammer was the original preparatory device, as shown in Curtis's 

 patent (13014 of 1850), which proposed the use of hammers falUng vertically 

 upon cane supported on an anvil. Searby's patents (U.S. 1 146464 and 

 1185005, 1916) adapt the swing hammer to the disintegration of cane. 

 This device, shown in Plate XXIII, includes a horizontal shaft, to which are 

 attached a series of loose hammers arranged six in any vertical plane. The 

 hammers are -i^-in. or |-in. by 2|-in., and the shaft makes 1,200 r.p.m., so 

 that 7,200 blows are struck on the 

 cane per minute. The result is to 

 separate complete!}' the fibro-vas- 

 cular bundles, and to reduce the 

 cane to a material of the nature of 

 " excelsior." 



This apparatus is preferably 

 used in conjunction with a crusher, 

 and is installed with the view of 

 increasing both capacity and ex- 

 traction. The independent results 

 reported from its use m Hawaii in 

 conjunction with 12-roller trains of 

 mill are very superior to those ob- 

 tained with anv other combination. 



e:-^ 



Fig. 141 



Crusher Rollers and Roll 

 Groovings. — The question whether 

 rollers should be smooth or grooved 

 is discussed in Tomlinson's " En- 

 cyclopaedia of Arts and Sciences," 

 published in 1854. 



The object of grooving rollers 

 is to increase the " gripping" area, 

 and thereby the capacity of the mill. 

 The modern practice is to use tri- 

 angular circumferential grooves, 



three to the inch, the grooves being pitched so as to mesh. The combi- 

 nation of the crusher and the mill in one unit seems to date from Aitken 

 and Mackie's patent (660 of 1907). This patent claims the surface of a 

 roller formed with a series of short ridges arranged at substantially 45° to 

 the axis, and each series at right angles to the adjacent series. The ridges 

 form a series of figures with triangular ends and trapezoidal sides. This 

 type has become well known as the " Diamond top roll crusher." Since it 

 appeared a large number of " figured " rollers, including a great variety of 

 geometrical patterns, have been patented. The adoption of these devices 

 has not become general. 



For an entirely different purpose are the drainage grooves introduced 



