Compared to the gyratory crusher, the cone crusher is characterized by its higher speed and a flat crushing chamber design, which is intended to give a high capacity and reduction ratio for materials suitable for this type of processing. The aim is to retain material longer in the crushing chamber to do more work on material as it is being processed (SME-AIME 1985). Figure 5.17 shows how stone flows through the crushing chamber of a cone crusher.
All crushers developed up to the 1920s, except for the very large gyratory crushers, were provided with some means of adjustment to compensate for wear or to adjust for variations in particle size. Generally, adjustments had to be made when the crusher was off line, but this was not a problem with machines that were used for coarse crushing to about 50-100 mm because the exact setting of the discharge opening was not critical and wear was slow. However, when it became necessary to crush to 10-25 mm, the setting of the smaller discharge opening had to be maintained within close limits, and the crusher was designed so that it could be adjusted mechanically without having to stop to reset the wearing parts. The design of the crushing chamber was also modified to suit the task. The fine-crushing Symons shorthead crusher has a chamber that is shorter and of slightly different shape than the standard coarser crusher, as shown in Figure 5.18.
The cone crusher has been widely used in the mining industry for 70 years to prepare feed for rod and ball mills and to crush critical-size pebbles that have been removed from autogenous or semiautogenous (SAG) mills because they are too small to be effective as grinding media and too large to be broken by the larger rocks. Its main use has been in the crushed-stone industry for producing aggregates to meet the demands set by the construction industries. Automated control systems have been developed to ensure that specifications for the various products are met.