Patent ID: 6715559
Filing Date: 2004-04-06
Classification: E21B

Abstract:
A method of preventing self-energizing of a gripper assembly for use with a tractor for moving within a passage, said gripper assembly configured to be longitudinally movably engaged with an elongated shaft of said tractor, said gripper assembly having an actuated position in which said gripper assembly substantially prevents movement between said gripper assembly and an inner surface of said passage, and a retracted position in which said gripper assembly permits substantially free relative movement between said gripper assembly and said inner surface of said passage, said gripper assembly having:an elongated mandrel longitudinally slidable with respect to said shaft of said tractor; a flexible toe with a first end portion and second end portion; a ramp having an inclined surface; and a roller rotatably secured to a center region of said toe, said roller configured to roll against said inclined surface of said ramp; wherein longitudinal movement of said ramp causes said roller to roll against said ramp between said inner and outer levels to vary the radial position of said center region of said toe, said method comprising: securing said first end portion to said mandrel with a first axle such that said first axle is longitudinally movable with respect to said first end portion; and securing said second end portion to said mandrel with a second axle such that said second axle is longitudinally movable with respect to said second end portion.