Patent ID: 6230813
Filing Date: 2001-05-15
Classification: E21B

Abstract:
A method of propelling a tool within a passage, the tool having a generally cylindrical body, a gripper including a plurality of gripper portions, and a switching apparatus all of said switching apparatus being within said tool, the method comprising:causing a first gripper portion to assume a first position in which said first gripper portion engages an inner surface of said passage and limits movement of said first gripper portion relative to said inner surface;moving said body with respect to said first gripper portion when said first gripper portion is in said first position;causing said first gripper portion to assume a second position in which said first gripper portion permits substantially free relative movement between said first gripper portion and said inner surface;causing a second gripper portion to assume a first position in which said second gripper portion engages an inner surface of said passage and limits movement of said second gripper portion relative to said inner surface;moving said body with respect to said second gripper portion when said second gripper portion is in said first position;causing said second gripper portion to assume a second position in which said second gripper portion permits substantially free relative movement between said second gripper portion and said inner surface;selectively continuously pulling and thrusting said body with respect to at least one gripper portion of said gripper in said first position; andsaid switching apparatus automatically switching the first gripper portion and the second gripper portion between the first position and the second position at any timewhen predetermined conditions occur within and/or immediately external to said tool.