Jaw Crusher are designed to impact on a rock

Jaw Crusher are designed to impact on a rock particle placed between a fixed and a moving plate. The jaw crusher faces of the plates are made of hardened steel. Both plates could be flat or the fixed plate flat and the moving plate convex. The surfaces of both plates could be plain or corrugated. The moving plate applies the force of impact on the particles held against the stationary plate. Jaw crusher Both plates are bolted on to a heavy block.
The moving plate is pivoted at the top end or at the bottom end and connected to an eccentric shaft. In universal jaw crusher the plates are pivoted in the middle so that both the top and the bottom ends can move.
The jaw crusher are single or double toggle drives. The function of the toggle is to move the pivoted jaw. The retrieving action of the jaw from its furthest end of travel is by springs for small crushers or by a pitman for larger crushers. As the reciprocating action removes the moving jaw away from the fixed jaw the broken rock particles slip down, but are again caught at the next movement of the swinging jaw and crushed.
This process is repeated until the particles sizes are smaller than the smallest opening between the crusher plates at the bottom of the jaw crusher. For a smooth reciprocating action of the moving jaws, heavy flywheels are used in both types of  jaw crusher.