| 摘要 |
An apparatus is provided. The apparatus comprises a housing, a body defining a first chamber and an elongate actuator member mounted for reciprocal movement, at least a part of the actuator member being enclosed by the housing. The apparatus further comprises a seal compartment between the first chamber and a compartment of the housing, the actuator member extending from the housing to the first chamber through the seal compartment. The seal compartment comprises a fluid filled seal chamber enclosing at least a portion of the actuator member and located within the housing, wherein a volume comprising a volume between the fluid filled seal chamber and the actuator member remains substantially constant during movement of the actuator member.
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