Roll crushers consist of two or more adjacent rolls placed parallel to each other and rotated in opposite directions. Single roll crushers are also available which rotate a single roll against a fixed breaker plate. Mineral or rock particles placed between the rolls are nipped and then crushed as they pass between the rolls. Rolls are held against each other by springs.
2. Design of Roll Crusher
Two types of roll crushers are generally designed. In the first type, both rolls are rigidly fixed to a frame with provision for adjusting the lateral position of one of the rolls to control the gap between them. Once set these rolls are locked into place. One roll is attached to the driving mechanism while the other rotates by friction. Single roll crushers are also available which rotate a single roll against a fixed breaker plate. In the second type, at least one roll is spring mounted which forms the driving roll, the other roll rotates by friction (following Figure). The nest of springs helps to provide uniform pressure along the length of the rolls. The springs are helical and pressure varies with the size of crusher and could be as high as 6 t/m (about 8300 kPa). In some roll crushers the rolls are individually driven. The drive is either by gears or belt. Both rolls usually rotate at the same speed but some crushers are designed such that one roll could rotate faster than the other. For fine grinding both rolls are rigidly fixed to the base, and therefore, they do not permit any movement of the rolls during operation. The surfaces of the rolls are smooth, corrugated or ribbed. Heavy duty toothed rollers are sometimes used as primary crushers, but the use of such rollers in the metallurgical industry is very limited. Read more