MAGNETOSTRICTIVE ACTUATOR

摘要

This invention relates to a magnetostrictive actuator, in particular for a percussive rock drill. The actuator comprises an applicator (4, 10, 11) with a magnetostrictive unit (4) having a length of magnetostrictive material and drive means for subjecting the material to a pulsed magnetic field to produce a change in the length of the material on each pulse of the magnetic field. The drive means has a plurality of coils supplied in parallel with an electric drive current pulsed at a drive frequency from one or more drive circuits. A biasing ram (10) may apply a compressive force along the length of the magnetostrictive material to bias a drill bit (2) against the rock (1).