Patent ID: 7954563

Claim:
A method of gripping a surrounding surface with an expandable assembly for use with a tractor for moving within a passage, said expandable assembly configured to be longitudinally movably engaged with an elongated shaft of said tractor, said expandable assembly comprising a first link, a second link, a wall engaging member, a roller and a ramp, the first and second links being pivotally attached relative to the elongated shaft at respective first ends and being connected with the wall engaging member at respective second ends, the roller and ramp being positioned such that the roller engages the ramp during at least a portion of a range of expansion of the expandable assembly, the method comprising the steps of: advancing the first end of the second link toward the first end of the first link such that the expandable assembly expands radially outwardly relative to the elongated shaft; fixing the first end of the first link against longitudinal movement along the elongated shaft of said tractor; engaging the surrounding surface with the wall engaging member under the influence of the expanding expandable assembly; after fixing the first end of the first link against longitudinal movement along the elongated shaft of said tractor, advancing the roller over at least a portion of the ramp such that a radially-outward force is applied to the wall engaging member.