Gripper assembly for downhole tools

A gripper assembly for use with a tractor for moving within a passage, said gripper assembly being longitudinally slidable along 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 comprising:

• an elongated mandrel configured to be longitudinally slidable with respect to said shaft of said tractor;
• a first toe support longitudinally fixed with respect to said mandrel;
• a second toe support longitudinally slidable with respect to said mandrel;
• a flexible elongated toe having a first end pivotally secured with respect to said first toe support and a second end pivotally secured with respect to said second toe support;
• a ramp having an inclined surface extending between an inner radial level and an outer radial level, said inner radial level being radially closer to the surface of said mandrel than said outer radial level, said ramp longitudinally slidingly engaged with said mandrel;
• and
• a roller rotatably secured to a center region of said toe, said roller configured to roll against 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 between a radially inner position corresponding to said retracted position of said gripper assembly and a radially outer position corresponding to said actuated position of said gripper assembly.

A gripper assembly for use with a tractor for moving within a passage, said tractor having an elongated shaft, 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 comprising:

• an elongated mandrel configured to be longitudinally slidable with respect to said shaft of said tractor;
• a first toe support longitudinally fixed with respect to said mandrel;
• a second toe support longitudinally slidable with respect to said mandrel;
• a flexible toe having a first end pivotally secured with respect to said first toe support and a second end pivotally secured with respect to said second toe support;
• a piston longitudinally slidable with respect to said mandrel;
• a ramp on an inner surface of said toe, said ramp sloping from a first end to a second end, said second end being radially closer to the surface of said mandrel than said first end;
• a slider element longitudinally slidable with respect to said mandrel and longitudinally fixed with respect to said piston;
• and
• a roller rotatably fixed with respect to said slider element, said roller configured to roll against said ramp;
• wherein said ramp is oriented such that longitudinal movement of said slider element causes said roller to roll against said ramp to vary the radial position of said center region of said toe between a radially inner position corresponding to said retracted position of said gripper assembly and a radially outer position corresponding to said actuated position of said gripper assembly, said piston and said slider element being movable between first and second longitudinal positions relative to said mandrel, such that when said piston and said slider element are in said first position said first end of said ramp bears against said roller and said gripper assembly is in said retracted position, and such that when said piston and said slider element are in said second position said second end of said ramp bears against said roller and said gripper assembly is in said actuated position.

A gripper assembly for use with a tractor for moving within a passage, said tractor having an elongated shaft, 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 comprising:

• an elongated mandrel configured to be longitudinally slidable with respect to said shaft of said tractor;
• a first toe support longitudinally fixed with respect to said mandrel;
• a second toe support longitudinally slidable with respect to said mandrel;
• a flexible elongated toe having a first end pivotally secured with respect to said first toe support and a second end pivotally secured with respect to said second toe support;
• a slider element longitudinally slidable with respect to said mandrel, said slider element being longitudinally slidable between first and second positions;
• and
• one or more elongated toggles having first ends rotatably maintained on said slider element and second ends rotatably maintained on a center region of said toe, said one or more toggles adapted to rotate between a retracted position in which said second ends of said one or more toggles and said center region of said toe are at a radially inner level that defines said retracted position of said gripper assembly, and an actuated position in which said second ends of said one or more toggles and said center region of said toe are at a radially outer level that defines said actuated position of said gripper assembly;
• wherein longitudinal movement of said slider element causes longitudinal movement of said first ends of said one or more toggles and thereby rotates said one or more- toggles, wherein when said slider element is in said first position said one or more toggles are in said retracted position, and when said slider element is in said second position said one or more toggles are in said actuated position.

A gripper assembly for anchoring a tool within a passage and for assisting movement of said tool within said passage, said gripper assembly being movable along an elongated shaft of said tool, 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 comprising:

• an elongated mandrel surrounding and configured to be longitudinally slidable with respect to said shaft of said tractor;
• a first toe support longitudinally fixed with respect to said mandrel;
• a second toe support longitudinally slidable with respect to said mandrel;
• a flexible elongated toe having a first end pivotally secured with respect to said first toe support and a second end pivotally secured with respect to said second toe support so that said first and second ends of said toe have an at least substantially constant radial position with respect to a longitudinal axis of said mandrel;
• a first interaction surface longitudinally slidable with respect to said mandrel, said first interaction surface being longitudinally slidable between a retraction position and an actuation position;
• and
• a second interaction surface on a central region of said toe, configured to interact with said driver;
• wherein longitudinal movement of said first interaction surface causes interaction between said first and second interaction surfaces substantially without sliding friction therebetween, said interaction varying the radial position of said central region of said toe, wherein when said first interaction surface is in said retraction position said central region of said toe is at a first radial distance from said longitudinal axis of said mandrel and said gripper assembly is in said retracted position, and when said first interaction surface is in said actuation position said central region of said toe is at a second radial distance from said longitudinal axis and said gripper assembly is in said actuated position.

A failsafe assembly for retracting a gripper portion of a downhole tool from an inner surface of a passage, said gripper portion having an actuated position in which said gripper portion substantially prevents movement between said gripper portion and said inner surface, and a retracted position in which said gripper portion permits substantially free relative movement between said gripper portion and said inner surface, said failsafe assembly comprising:

• a piston configured to control the actuation and retraction of said gripper portion, said piston having an actuation position in which said gripper portion is in its actuated position, said piston having a retraction position in which said gripper portion is in its retracted position;
• an actuation chamber configured so that fluid in said actuation chamber exerts a pressure force on said piston which tends to move said piston to said actuation position;
• a retraction chamber configured so that fluid in said retraction chamber exerts a pressure force on said piston which tends to move said piston to said retraction position;
• a high pressure fluid chamber;
• an exhaust chamber in fluid communication with the exterior of said tool;
• a failsafe valve in fluid communication with said actuation, retraction, high pressure, and exhaust chambers, said failsafe valve having a first position in which said failsafe valve permits fluid communication between said high pressure fluid chamber and said actuation chamber and also between said retraction chamber and said exhaust chamber, said failsafe valve having a second position in which said failsafe valve permits fluid communication between said high pressure fluid chamber and said retraction chamber and also between said actuation chamber and said exhaust chamber, said failsafe valve having a surface exposed to said high pressure fluid chamber so that fluid in said high pressure fluid chamber exerts a pressure force onto said surface of said failsafe valve which tends to move said failsafe valve to said second position thereof;
• a restraint in contact with said failsafe valve and configured to maintain said failsafe valve in said first position thereof so that said failsafe valve will remain in said first position until said pressure force onto said surface of said failsafe valve exceeds a threshold pressure;
• wherein when said failsafe valve is in said first position thereof and when fluid pressure in said high pressure fluid chamber exceeds said threshold pressure, said failsafe valve moves to said second position thereof so that fluid in said high pressure fluid chamber flows into said retraction chamber to move said piston to said retraction position and said gripper portion to said retracted position thereof, and so that fluid in said actuation chamber flows to said exhaust chamber.