How Does a Rock Crusher Work?

Rock crushers break down ore.
••• ore image by Antons Trifonovs from

Rock Crushers Defined

A rock crusher is a device used to crush rocks into smaller pieces, usually for gravel or some other road or building application. Most rock crushers have a hopper at the top -- a container which holds the rock above the crusher and uses gravity to feed it in. Alternately, rock crushers can use a belt drive to continuously transport the rock into the crusher. At the bottom of nearly every type of crusher is a hole. Once a rock has been pressed into small enough pieces to fit through the hole, it exits the crusher either onto, a conveyor belt, into a bin or onto a large pile. In some cases, one rock crusher may feed directly into a second one, crushing the rocks up into finer and finer particles in two or three stages.

Jaw Crusher

Jaw crushers are the oldest and one of the simplest sorts of rock crushers. A jaw crusher is like a giant collapsible V made out of two metal walls. At the bottom, the two walls are very close together and at the top they are further apart. One wall is held still while the other is closed against it -- usually about three times a second. When it closes, the jaw crushes the rocks inside it. Because it tapers, the rocks are crushed to smaller and smaller sizes as they go down, then dropped through the bottom.

Roller Crusher

Another common type is the roller crusher. The roller crusher is a set of two large metal rolers rotating in opposite directions. Rocks are fed into the space between the two rollers, where they are crushed and then dropped to the ground. Roller crushers are often used as a secondary crushing stage. Small, pre-crushed rocks are inserted into the roller, which then breaks them down into gravel.

Gyratory and Stone Crushers

Gyratory and cone crushers work in pretty much the same way, although they have slightly different designs. The rock falls into the top of a chamber with a spinning grinder at the bottom. As the rock falls down, it is squeezed between the grinder and the walls of the chamber and crushed. As it continues to fall down the chamber, it is pulverized into smaller and smaller bits until it falls out the bottom.

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