. Cement and concrete. y centrifugal force againstthe inner surface of the ring where the grinding takes place, andthus runs around the ring in a direction opposite to thatin which the pulley is revolved. The material which dropsbelow the roller is thrown up again by steel blades attachedto the bottom of the shaft, and above the roller are fans whichcreate a draft, forcing the finished product through the screensabove the ring whence it falls into a hopper. Although therepair expenses of a Griffin mill are high, it has proved a verysatisfactory machine and is extensively used, especially for t
. Cement and concrete. y centrifugal force againstthe inner surface of the ring where the grinding takes place, andthus runs around the ring in a direction opposite to thatin which the pulley is revolved. The material which dropsbelow the roller is thrown up again by steel blades attachedto the bottom of the shaft, and above the roller are fans whichcreate a draft, forcing the finished product through the screensabove the ring whence it falls into a hopper. Although therepair expenses of a Griffin mill are high, it has proved a verysatisfactory machine and is extensively used, especially for thefinal reduction of clinker. The size of mill is designated bythe diameter of the ring or die. A 36-inch mill, with roller 24inches in diameter, 6-inch face, and weighing 175 pounds,consumes 25 to 35 and grinds 8 to 10 barrels of cementper hour when working on clinker not coarser than one-halfinch. The manufacturers of the Griffin mill now make a 3-rollmill of somewhat similar construction. 30 CEMENT AND CONCRETE. 30-INCH GRIFFIN MILL ARRANGED FOR DRY PULVERIZING GRINDING 31 The Huntington Mill is very similar to the Griffin mill, thesingle roller of the latter being replaced by three rolls suspendedfrom a revolving head. As the head is revolved, the rolls pressagainst the steel ring surrounding them, and by reason of thiscontact the rolls revolve upon their shafts. The output andpower consumption are said to be about the same as in theGriffin mill. The Fuller-Lehigh Pulverizer Mill is a more recent style ofgrinder, said to be suitable for Portland cement clinker as wellas raw material and coal. The machine consists of an up-right horizontal ring or die with a circular groove or track inwhich travel four balls. The balls rest upon a horizontalannular plate the revolution of which causes the balls to revolveand press against the circular track. The die, plate and ballsare of Swedish iron. The balls are 9j inches in diameter andweigh 112 pounds each, and as they revolve at
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