| 摘要 |
A lock for selectively allowing and preventing longitudinal displacement of an outer and inner telescoping tube segments comprises a plug member fastened to one end of the inner tube segment which includes a S-shaped cam projecting outwardly for cooperating with a pair of cam followers that are shaped so that when the inner tube segment is rotated in a first direction relative to the outer one, the two cam followers are drawn out of contact with the inside surface of the outer tube segment. When the inner tube is rotated in the opposite direction, the cam forces the cam followers radially outward so as to abut with substantial friction the inner surface of the outer tube segment.
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