| 摘要 |
An apparatus (20) includes a housing (90) and a longitudinal member (80) movable in opposite directions relative to the housing. A first cam (176) is pivotable relative to the housing (90). The first cam (176) is engageable with the longitudinal member (80) to prevent movement of the of the longitudinal member in a first direction relative to the housing (90). A second cam (186) is pivotable relative to the housing (90). The second cam (186) is engageable with the longitudinal member (80) to prevent movement of the longitudinal member in a second direction opposite the first direction relative to the housing (90). At least one spring (210) biases the first and second cams (176, 186) into engagement with the longitudinal member (80). An actuator (250) moves the first and second cams (176, 186) out of engagement with the longitudinal member (80) to permit movement of the longitudinal member relative to the housing (90).
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