Patent ID: 7195080

Claim:
A system for increasing the diameter of at least a portion of a well bore, said system being intended to be attached to a drill pipe, said system comprising: a longitudinal substantially cylindrical body extending in a longitudinal direction, said body being provided with means adapted for attaching said body to the drill pipe and having at least one chamber and two openings; a support element movably mounted with respect to the body in the longitudinal direction of the body, said support comprising a first shaft and a second shaft parallel to each other and perpendicular to the longitudinal direction of the body, said element being located in the chamber of the body; first and second arms provided with cutting means, the first arm being pivotably mounted on the support element around an axis of pivotment perpendicular to the longitudinal direction of the body, while the second arm is pivotably mounted on the support element around an axis of pivotment parallel to the axis of pivotment of the first arm, each arm pivoting with respect to the support element between a first position in which the arm extends in the chamber and a second position in which at least a portion of the cutting means extends outside the chamber after passing through an opening of the body; and a blocking means provided with at least a first abutment portion and a second abutment portion, said means being movably mounted with respect to the body in the longitudinal direction of the body; in which each of said first and second arms when located in the chamber has at least one first face directed towards the longitudinal axis of the body and at least one second face directed opposite to the longitudinal axis of the body, in which the chamber of the body has a first face inclined with respect to the longitudinal direction of the body, said first face of the chamber acting as an abutment contacting the second face of the first arm when said first arm extends in said second position, and a second face inclined with respect to the longitudinal direction of the body, said second face of the chamber acting as an abutment contacting the second face of the second arm when said second arm extends in said second position, and in which the first abutment portion of the blocking means has an abutment face parallel to the first face of the first arm and contacting said first face of the first arm, when said first arm extends in said second position, while the second abutment portion of the blocking means has an abutment face parallel to the first face of the second arm and contacting said first face of the second arm, when said second arm extends in said second position.