Working Principle of a Rock Breaker

How about this bad boy?

Rock breaker mainly breaks the rock with the to & fro motion of hammer at a particular speed of motion . I dont know the technical name of that hammer. Hammer also have chiselled /slanted edges for effective breaking. The hammer is mounted on a big frame. The actuation is done by a hydraulic system , which uses a spool piece , actuated by particular grade of oil and solenoid V/'s . This brings abbout the to& fro motion. the speed & travel of hammer is variable. The system is very much similar to all earth moving equiments like Excavator loader, etc.