Caterpillar Inc.
CONTROL SYSTEM FOR DRILLING MACHINES

Abstract:

A control system for a drilling machine includes a vertically movable and rotatable drill string having a drill bit at a distal end, a hydraulic cylinder coupled to the drill string to provide a motive force for the vertical movement of the drill string, the hydraulic cylinder having an extend chamber and a retract chamber, a counterbalance valve selectively opening to fluidly couple the retract chamber to a drain, and a holdback valve selectively controlled to adjust the opening of the counterbalance valve based on a weight of the drill string.