Journal . ressurewould start the oil, making a greasy mass. Theyconsist of two chilled iron or porcelain rollers,sometimes of equal size, sometimes one large andone small, either plain or, if there is any difficulty ingetting a grip on the material, fluted or spiked; whilstfor crushing material such as sugar cane they oftenresemble spur gears. Init are verj wide comparedwith their diameter. Sometimes the rollers arecompounded, being four or five high, the materialpassing between the first and second rolls, backagain between second and tlurd, again betweenthird and fourth, and so on ; this meth
Journal . ressurewould start the oil, making a greasy mass. Theyconsist of two chilled iron or porcelain rollers,sometimes of equal size, sometimes one large andone small, either plain or, if there is any difficulty ingetting a grip on the material, fluted or spiked; whilstfor crushing material such as sugar cane they oftenresemble spur gears. Init are verj wide comparedwith their diameter. Sometimes the rollers arecompounded, being four or five high, the materialpassing between the first and second rolls, backagain between second and tlurd, again betweenthird and fourth, and so on ; this method isadopted for paint roUiug and also for seed crushingbefore pressing for oU. Another method of addingto the efficiency of rolls is to supplement their Vol. XXXIV., No. 7.] CROSBIE—GRINDING AND CRUSHING MACHINERY. 323 purciv crushing action by reciprocating one or both•of the rolU-rs latiTally, or by passing the material•between a single roll ami a .shaped lilock, which is ^yrrm^ Rolli (Ccntr^ujal). 5^d AW/3 riiit<^ ftoi/i Fia. of various types. continually moved backwards and forwardsacross the face of the roll. This gives the requiredcombination of compression and shear necessaryfor tine grinding. Occasionally it happens that to crush a seed sothat every particle is fine enough for use entailsthe softer part being too finely crushed ; thisoccurs with malt for brewing, and in this case thegrain is given a preliminary nip through one pairof rolls, falling on to a sieve which separates thefine, while the coarse passes over the end of thesieve and tlirough another pair of rolls, giving amuch harder nip, crushing the rest rollers running at equal speeds the materialis only subjected to a squeeze or nip which tendsto flatten out a soft material rather than reduceits size, so differential rolls are used, where oneroller revolves faster than the other, imparting arubbing as well as a flattening action. Again,these rollers may be either plain or gr
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectchemist, bookyear1882
