Patent ID: 7080701
Filing Date: 2006-07-25
Classification: E21B

Abstract:
1. A tractor for moving within a passage, comprising: an elongated body; a propulsion container engaged with and movable with respect to the body, the propulsion container having an elongated interior volume defined between ends of the propulsion container; a thrust-receiving member fixed with respect to the body, the thrust-receiving member residing within and being movable between the ends of the propulsion container, the thrust-receiving member fluidly dividing the interior volume of the propulsion container into an aft chamber on an aft end of the thrust-receiving member and a forward chamber on a forward end of the thrust-receiving member; a first gripper assembly slidably engaged with the body, the first gripper assembly having an actuated position in which the first gripper assembly limits movement of the first gripper assembly relative to an inner surface of the passage and a retracted position in which the first gripper assembly permits substantially free relative movement of the first gripper assembly relative to the inner surface of the passage, the first gripper assembly having a first actuation chamber configured so that the first gripper assembly moves to its actuated position when pressurized fluid flows into the first actuation chamber, and so that the first gripper assembly moves to its retracted position when pressurized fluid flows out of the first actuation chamber; a second gripper assembly slidably engaged with the body, the second gripper assembly having an actuated position in which the second gripper assembly limits movement of the second gripper assembly relative to the inner surface of the passage and a retracted position in which the second gripper assembly permits substantially free relative movement of the second gripper assembly relative to the inner surface of the passage, the second gripper assembly having a second actuation chamber configured so that the second gripper assembly moves to its actuated position when pressurized fluid flows into the second actuation chamber, and so that the second gripper assembly moves to its retracted position when pressurized fluid flows out of the second actuation chamber; a high pressure chamber configured to receive pressurized fluid from a source external to the tractor; a propulsion control valve having a first position in which the propulsion control valve permits fluid to flow from the high pressure chamber through the propulsion control valve into the aft chamber of the propulsion container, and in which the propulsion control valve permits fluid in the forward chamber of the propulsion container to flow through the propulsion control valve into an annulus between the tractor and the inner surface of the passage, the propulsion control valve having a second position in which the propulsion control valve permits fluid to flow from the high pressure chamber through the propulsion control valve into the forward chamber of the propulsion container, and in which the propulsion control valve permits fluid in the aft chamber of the propulsion container to flow through the propulsion control valve into the annulus; a gripper control valve having a first position in which the gripper control valve permits fluid to flow from the high pressure chamber through the gripper control valve into the first actuation chamber to cause the first gripper assembly to move to its actuated position, and in which the gripper control valve permits fluid in the second actuation chamber of the second gripper assembly to flow through the gripper control valve into the annulus so that the second gripper assembly moves to its retracted position, the gripper control valve having a second position in which the gripper control valve permits fluid to flow from the high pressure chamber through the gripper control valve into the second actuation chamber to cause the second gripper assembly to move to its actuated position, and in which the gripper control valve permits fluid in the first actuation chamber of the first gripper assembly to flow through the gripper control valve into the annulus so that the first gripper assembly moves to its retracted position; a sensor configured to sense when the thrust-receiving member approaches an end of the interior volume of the propulsion container; and a control assembly responsive to the sensor, the control assembly configured to toggle the gripper control valve between its first and second positions and also to toggle the propulsion control valve between its first and second positions.