CPC Subgroup
E21B 1/22 driven by electromagnets
Full Title
Percussion drilling > with a reciprocating impulse member (E21B1/02, E21B1/38 take precedence) > driven by electromagnets
E21B 1/22 Percussion drilling > with a reciprocating impulse member (E21B1/02, E21B1/38 take precedence) > driven by electromagnets