This invention relates to convertible vertical shaft impactors, and more particularly to a vertical shaft impact crusher which can be converted between autogenous crushing and anvil crushing.
Impact crushers operate on the principle of accelerating the rock to a high speed and causing it to impact against a target which will cause the rock to fracture. There are essentially two types of impact crushers: autogenous impact crushers and anvil impact crushers. The autogenous variety uses a bed of the same material that is being broken or crushed as the target area so that the rock which is accelerated impacts against other rock of the same type. Anvil type impact crushers utilize a hard target such as manganese steel as the target area.
The autogenous and anvil types of impact crushers are used for different purposes. Autogenous crushing is used primarily for reshaping rock which is already approximately the right size. It is most frequently used on wash gravel or natural rock which is smooth and needs to be reshaped with flat faces so that it can be used as aggregate in concrete and the like. Autogenous crushing also produces a large number of fines so that most of the product of autogenous breaking or crushing is at the two extreme ends of the product size spectrum.
Anvil breaking, on the other hand, produces a shattering action on the rock so that the majority of the product is near the central region of the product size distribution spectrum. Anvil breaking is used primarily to reduce the size of the input rock rather than to reshape rock which is already approximately the correct size.
Impact rock crushers are often mounted on trailers for transportation from site to site so that rock may be crushed at the location where it is needed. However, in the past, it has been necessary to use an autogenous crusher for autogenous crushing and to use an anvil crusher for anvil crushing. This has increased the equipment capital costs substantially and reduced efficiencies which could have been obtained by using the same machine for both types of crushing.
By its very nature, a vertical shaft impact crusher tends to be a noisy and dusty machine. Excessive noise and dust severely degrade the work environment around a vertical shaft impactor and may become serious enough to run afoul of OSHA standards. In addition, a noisy and dusty environment reduces worker efficiency by increasing fatigue and decreasing worker attention span and patience so that they may tend to become careless about ordinary rules of safety and machine operation. The result can be an increase in machine malfunctions due to operator error and an increase in all types of absenteeism.
Thus, there has been a long-standing, unfulfilled need in the industry for a vertical shaft impact crusher that could be used for autogenous or anvil impact crushing by simple replacement of the breaker ring, which breaker ring could be adjustably mounted in the impact crusher at various vertical positions selected to optimize the operating parameters of the machine, and which contains structure for dust and noise abatement to achieve the best possible work environment around the machine.