Patent ID: 8302679

Claim:
A gripper assembly for anchoring a tool within a passage defining an axis and for assisting movement of said tool within said passage, said gripper assembly having a first configuration in which said gripper assembly substantially prevents movement between said gripper assembly and an inner surface of said passage, and a second configuration in which said gripper assembly permits relative movement between said gripper assembly and said inner surface of said passage, said gripper assembly comprising: an actuator; an expandable assembly coupled to the actuator such that the expandable assembly is selectively moveable between a retracted position and an expanded position, said expandable assembly comprising a first link and a second link, said first link having an end pivotably secured to an end of said second link; an engagement assembly having a first end, a second end, and a central area, the first and second ends being pivotally coupled to an elongated shaft such that the first and second ends maintain an at least substantially constant radial position with respect to a longitudinal axis of the elongated shaft, and the central area comprising a wellbore wall gripping portion that is configured to apply force against the inner surface of said passage in the first configuration, the first end being one of bifurcated such that the first end is pivotally coupled to the elongated shaft by two axles and trifurcated such that the first end is pivotally coupled to the elongated shaft by three axles, said gripper assembly further comprising a roller, wherein interaction between said roller and a roller engagement surface proximate said end of said first link and said end of said second link creates an outward force on said engagement assembly.