| 摘要 |
An actuator includes, a housing, an expandable member housed within the housing configured to expand and contract, an elongated member in operable communication with the expandable member, and a ratchet in operable communication with at least one of the expandable member and the elongated member. The ratchet is configured to allow movement of the elongated member in a first direction relative to the housing in response to expansion of the expandable member and to prevent movement of the elongated member in a second direction in response to contraction of the expandable member until the elongated member has moved a selected dimension, after which the ratchet automatically permits movement of the elongated member in the second direction.
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