Patent ID: 7900717

Claim:
An expandable reamer apparatus for enlarging a borehole in a subterranean formation, comprising: a tubular body having a longitudinal axis, an inner bore, an outer surface, and at least one track within the tubular body between the inner bore and the outer surface, the at least one track sloped upwardly and outwardly at an acute angle to the longitudinal axis; a drilling fluid flow path extending through the inner bore; one or more blades each having at least one cutting element configured to remove material from a subterranean formation during reaming, at least one blade slideably coupled to the at least one track of the tubular body; a push sleeve disposed within the inner bore of the tubular body and coupled to the at least one blade, the push sleeve configured to move axially upward responsive to a pressure of drilling fluid passing through the drilling fluid flow path to extend the at least one blade along the at least one track and into an extended position, the push sleeve having at least one retainment feature coupled thereto; and a traveling sleeve disposed at least partially within the push sleeve, the traveling sleeve configured to selectively retain the push sleeve in an initial position through contact with the at least one retainment feature coupled to the push sleeve.