CRUSHING MACHINERY. Perhaps this earliest form of crushing machine is the stamp or stamp mill, which is now so extensively employed in reducing gold, copper, and other ores. Briefly described, a stamp mill consists of one or more stamps beneath which the ore is fed in a thin stream. Each stamp consists of a stem carrying at its lower end a head of chilled cast iron and arranged to work vertically up and down be tween guides. To produce the vertical movement there is a bracket or lug attached to the stem with which a cam or series of cams mounted on horizontal shafting engages, and thus raises and releases the stamp. In reducing ores stamps are usually operated in batteries or groups. Stamp mills perform either coarse or compara tively fine crushing, according as the rate of feed is fast or slow. Sometimes positive pressure stamps are employed in place of gravity stamps. Roll crushers are another important type. In them the material to be crushed is passed be tween two or more vertical rolls which may or may not have corrugated surfaces. Sometimes the rolls arc designed to have a slipping action with reference to each other. Boll crushers are used in crushing sugar-cane and other fibrous materials particularly. crushers are usually employed in crushing seeds for oil. Generally they consist. of a vertical axle which carries two or more radial arms, on the ends of which are journaled heavy metal wheels with broad tires or edges. These wheels through the rotation of the vertical nxle travel round and round in a circular track on the bottom of a shallow pan, into which the materials to be crushed are thrown. The crushing is done by the
heavy wheel passing over the material. Jaw crushers, or reciprocating crushers, are one of the kinds most commonly used. They consist of two jaws, one fixed and one movable, so ar ranged as to form a V-shaped opening between them. This V-shaped jaw is not closed at the bottom, and one of the jaws is hinged at the top and so connected with suitable mechanism that it is alternately pushed toward and drawn away from the fixed jaw, thus alternately en larging and reducing the V-shaped opening be tween the two. The material to be crushed, stone or ore, is inserted into the top of the jaw open ing and is crushed by the reciprocating motion of the movable jaw until fine enough to run out of the bottom opening.
by a vertical shaft which has simple rotary mo tion without gyration.
Sausage-mill crushers consist of a longitudinal shaft carrying radial teeth working inside a cylindrical shell, from whose inner surfaces pro ject radial teeth between which the shaft teeth mesh during revolution. All of these principal types of crushers are made in several forms, for each of which special qualities are claimed by the manufacturers. Stamp mills are almost ex elusively used for crushing metal-bearing ores; roll and edge-runner crushers for crushing fibrous materials; and jaw and gyratory crushers for crushing ores, rock, cement, phosphate, and similar hard materials.