Jaw and Rolls Crushers for Stone Produced
Even though the setting of the discharge opening of a crusher will determine the maximum-size stone produced, the aggregate sizes will range from slightly greater than the crusher setting to fine dust. For any given setting for jaw or roll crusher approximately 15% of the total amount passing through the crusher will be larger than the setting.
If the opening of the screen which receives the output from such crusher are the same size as the crusher setting, 15% of the output will not pass through the screen. Figure 1 (Figure 14.4, Text) provides the percent of material passing or retained on screens having the size opening indicated.
Major Jaw Crushers
Jaw crushers operate by allowing stone to flow into the space between two jaws, one of which is stationary while the other is movable.
The distance between the jaws diminishes as the stone travels downward under the effect of gravity and the motion of the movable jaw, until the stone ultimately passes through the lower opening.
Jaw crushers are usually designed with the toggle as the weakest part. The toggle will break if the machine encounters an uncrushable object or is subjected to overload. This limits damage to the crusher. In selecting a jaw crusher, consideration must be given to the size of the feed stone.
Gyratory Crushers
Gyratory crushers are characterized by a gyrating mantle mounted within a deep bowl. Gyratory crushers provide continuous crushing action and are used for both primary and secondary crushing of hard, tough, abrasive rock.
Gyratory Standard Cone Crusher
Cone crushers are used as secondary or tertiary crushers. Cone crushers are capable of producing large quantities of uniformly fine crushed stone. A cone crusher differs from a true gyratory crusher in the following respects:
- It has a shorter cone.
- It has a smaller receiving opening.
- It rotates at a higher speed, about twice that of a true gyratory.
- It produces a more uniformly sized stone.
Roll Crushers
Roll crushers are used for producing additional reductions in the sizes of stone after the output of a quarry has been subjected to one or more stages of prior crushing.
A roll crusher consists of a heavy cast- iron frame equipped with either one or more hard-steel rolls, each mounted on a separate horizontal shaft.
Production Of Crushed Stone
In operating a quarry and crushing plant, the drilling pattern, the amount of explosives, the size shovel or loader used to load the stone, and the size of the primary crusher should be coordinated to assure that all stone from the quarry can be economically utilized.
