| 摘要 |
<p>An electrically powered and controlled tractor system includes one or more electric gripper assemblies (20) and one or more electric power train assemblies (30). Power and control signals for the gripper assemblies (20) and power train assemblies (30) can be delivered from a ground surface via a wireline (40). The gripper assembly (20) employs a motor-activated lead screw (216) and nut (214) combination to expand passage-gripping elements (206), preferably by pushing the gripping elements (206) radially outward from locations between opposing ends (207) of the gripping elements (206). A failsafe mechanism can retract the gripping elements (206) during a power interruption. The power train assembly (30) employs a motor-activated lead screw (312) and nut (314) combination to expand and contract two ore more telescoping members (302, 304, 306). The tractor system can include multiple tractor units (10) that each includes one gripper assembly (20) and one power train assembly (30). A tractor (700) can include one power train assembly (720) and two gripper assemblies (730).</p> |
