Patent ID: 8327954

Claim:
A drilling apparatus comprising: a tubular body comprising an upper connection and a lower connection with a drill bit disposed thereon, and an axial borehole therethrough, wherein the upper connection is configured to attach to a drillstring; primary cutter blocks coupled to the tubular body and configured to selectively expand radially therefrom; backup cutter blocks coupled to the tubular body and configured to selectively expand radially therefrom; and an activation system, which in response to changes in weight on the primary and backup cutter blocks, is configured to: expand the primary cutter blocks and collapse the backup cutter blocks in a first operation sequence; and collapse the primary cutter blocks and expand the backup cutter blocks in a second operation sequence; wherein the activation system comprises: at least one sensor operatively coupled to a motor; a pump operatively coupled to the motor; a ball-drop sleeve fixed relative to a main sleeve with at least one shear pin; wherein the main sleeve is configured to move within the axial borehole of the drilling apparatus to open and close a primary cutter block activation ort and a backup cutter block activation port.