초록 ▼

A gripper for use in a downhole tool is provided. The gripper can include an actuator, a toe assembly, and an expandable assembly. The toe assembly can be a leaf-spring like elongate continuous beam. The expandable assembly can be a linkage including a plurality of links. The linkage is coupled to t

A gripper for use in a downhole tool is provided. The gripper can include an actuator, a toe assembly, and an expandable assembly. The toe assembly can be a leaf-spring like elongate continuous beam. The expandable assembly can be a linkage including a plurality of links. The linkage is coupled to the actuator such that the actuator expands the expandable assembly which in turn expands the toe assembly. In operation, during one stage of expansion radial forces are transmitted to the toe through both interaction of a rolling mechanism on the toe with the expandable assembly and pressure of the linkage assembly directly on an inner surface of the toe.

대표청구항 ▼

What is claimed is: 1. A gripper assembly having an actuated position in which said gripper assembly substantially prevents movement between said gripper assembly and an inner surface of a passage, and a retracted position in which said gripper assembly permits substantially free relative movement

What is claimed is: 1. A gripper assembly having an actuated position in which said gripper assembly substantially prevents movement between said gripper assembly and an inner surface of a 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 comprising: an actuator configured to selectively move the gripper assembly between the actuated position and the retracted position; an expandable assembly comprising a plurality of segments pivotally connected in series, the expandable assembly coupled to the actuator such that the expandable assembly is selectively moveable between a retracted position in which a longitudinal axis of the expandable assembly is substantially parallel with an elongated shaft along which the gripper assembly is moveable and an expanded position in which the segments of the expandable assembly are buckled radially outward with respect to the elongated shaft; a toe having a first end, a second end, and a central area, the first and second ends being pivotally coupled to the 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 being radially expandable with respect to the elongated shaft such that an expanded position of the toe corresponds to the actuated position of the gripper assembly and a retracted position of the toe corresponds to the retracted position of the gripper assembly; a roller mechanism rotatably coupled to an inner surface of the central area of the toe, the roller mechanism configured to interface with an outer surface of one of the plurality of segments of the expandable assembly such that as the expandable assembly is buckled by the actuator, the roller mechanism is advanced up the one of the plurality of segments and the toe is expanded. 2. The gripper assembly of claim 1, wherein the outer surface of the one of the plurality of segments has a curved profile. 3. The gripper assembly of claim 1, further comprising a ramp pivotally coupled to the outer surface, wherein the roller mechanism moves against said ramp for at least a portion of a movement of the gripper assembly between the retracted position and the actuated position. 4. The gripper assembly of claim 1, wherein at least one of the first end and the second end of the toe is bifurcated such that the bifurcated end is pivotally coupled to the elongated shaft by at least two axles. 5. The gripper assembly of claim 4, wherein in operation the gripper assembly is configured such that the first end of the elongated toe is positioned uphole of the second end relative to the passage and wherein the first end of the elongated toe is bifurcated. 6. The gripper assembly of claim 4, wherein the first end of the elongated toe and the second end of the elongated toe are bifurcated. 7. The gripper assembly of claim 4, wherein at least one of the first end and the second end is trifurcated such that the trifurcated end is pivotally coupled to the elongated shaft by three axles. 8. The gripper assembly of claim 1, wherein the plurality of segments defines a link assembly comprising: a first link having a first end and a second end, the first end being pivotally coupled to the actuator; and a second link having a first end and a second end, the first end being pivotally coupled to the second end of the first link, and the second end being pivotally and slidably coupled to the elongated shaft; and wherein the second link defines the one of the plurality of segments having the outer surface with which the roller mechanism is configured to interface. 9. The gripper assembly of claim 8, wherein a length of the second link is greater than a length of the first link. 10. The gripper assembly of claim 8, wherein the outer surface of the second link has an arcuate profile. 11. The gripper assembly of claim 10, wherein the actuate profile of the outer surface of the second link has a radius of curvature, wherein the second link has a length from the first end to the second end, and wherein a ratio of the radius of curvature of the actuate profile of the outer surface of the second link to the length of the second link is between approximately 1.75:1 and approximately 2.5:1. 12. The gripper assembly of claim 8, wherein the first end of the first link and the second end of the second link are positioned at an angular offset with respect to each other such that advancement of the first end of the first link along the elongated shaft toward the second end of the second link tends to buckle the link assembly radially outward from the elongated shaft. 13. The gripper assembly of claim 8, further comprising a buckling mechanism configured to buckle the link assembly radially outward from the elongated shaft during expansion of the gripper assembly. 14. The gripper assembly of claim 13, wherein the buckling mechanism comprises a buckling pin positioned on one of the toe and the link assembly, and a flange configured to interface with the buckling pin and positioned on the other of the toe and the link assembly. 15. The gripper assembly of claim 8, wherein at least one of the first link and the second link are comprised of inconel. 16. The gripper assembly of claim 15, wherein the first link is pivotally coupled to the second link with a tungsten carbide pin. 17. The gripper assembly of claim 1, wherein the actuator includes a failsafe to bias the gripper assembly in the retracted position. 18. The gripper assembly of claim 1, wherein the gripper assembly is configured to generate radial force over an expansion range between the retracted position and the actuated position of the gripper assembly and expansion of the gripper assembly comprises: a first stage in which radial force is generated by the roller mechanism advancing up a ramp coupled to the outer surface of the one of the plurality of segments; a second stage in which radial force is generated by interaction of the roller mechanism with the outer surface of the one of the plurality of segments and by radial movement of a first end of the one of the plurality of segments with respect to a second end of the one of the plurality of segments; and a third stage in which radial force is generated by interaction of the roller mechanism with the outer surface of the one of the plurality of segments. 19. The gripper assembly of claim 18, wherein the first stage of the expansion range spans from an expanded diameter of approximately 3.7 inches to approximately 4.1 inches. 20. The gripper assembly of claim 18, wherein the second stage of the expansion range spans from an expanded diameter of approximately 4.1 inches to approximately 5.76 inches. 21. The gripper assembly of claim 18, wherein the third stage of the expansion range spans from an expanded diameter of approximately 5.76 inches to approximately 6.5 inches. 22. The gripper assembly of claim 18, wherein a ratio of a first radial expansion distance defined by a total radial expansion of the first stage of the expansion range to a second radial expansion distance defined by a total radial expansion of the second stage of the expansion range is between approximately 1:2 and approximately 1:4. 23. The gripper assembly of claim 18, wherein a ratio of a second radial expansion distance defined by a total radial expansion of the second stage of the expansion range to a third radial expansion distance defined by a total radial expansion of the third stage of the expansion range is between approximately 2:1 and approximately 1.5:1. 24. The gripper assembly of claim 23, wherein a ratio of a first radial expansion distance defined by a total radial expansion of the first stage of the expansion range to the second radial expansion distance is between approximately 1:2 and approximately 1:4. 25. A method of at least temporarily achieving anchoring within a passage, the method comprising: providing a gripper comprising a radially expandable toe having a roller mechanism positioned on the radially inward side of the toe and an expandable assembly comprising a plurality of segments pivotally coupled in series and positioned radially inward of the toe, the expandable assembly configured to radially expand the toe by interfacing with the roller mechanism; generating radial expansion force at the toe, wherein generating radial expansion force comprises: advancing the roller mechanism on the toe along an outer surface of a first segment of the expandable assembly; buckling the expandable assembly such that one end of the first segment is moved radially outward; and engaging the gripper with an inner surface defining the passage to anchor the gripper within the passage. 26. The method of claim 25, wherein the step of buckling the expandable assembly further comprises: buckling the expandable assembly such that a first end of a second segment of the expandable assembly is moved radially outward, wherein the first end of the second segment is pivotally coupled to the first segment and the second segment is relatively short in an axial direction relative to the first segment. 27. A method of at least temporarily achieving anchoring within a passage, the method comprising: providing a gripper comprising a radially expandable toe and a link assembly positioned radially inward of the toe and configured to radially expand the toe; generating radial expansion force over a first expansion range by advancing a roller mechanism on the toe of the gripper up a ramp coupled to a link of the link assembly; generating radial expansion force over a second expansion range by advancing the roller mechanism over an outer surface of a link of the link assembly and by buckling of the link assembly radially outward respect to the tool; generating radial expansion force over a third expansion range by advancing the roller mechanism over an outer surface of the link assembly; and engaging the gripper with an inner surface defining the passage to anchor the gripper within the passage.