| 摘要 |
A retractable bollard 100 comprising an embedded outer housing 10 having an open end and a closed end, a ram 20 slidably mounted within the outer housing 10, the ram 20 having an outer surface, and means for injecting fluid into, and means for removing fluid from, a chamber 24 within the retractable bollard 100 to move the ram 20 relative to the outer housing 10 between a retracted position and an extended position. The outer surface of the ram 20 is exposed to the surroundings of the bollard 100 when the ram 20 is in the extended position. The chamber 24 is bounded by at least one surface of the ram 20, one or more sliding surfaces and one or more seals 43a, 43b configured to move in sealing relationship relative to the sliding surfaces. The ram 20 is able to be completely removed from the outer housing 10 without separating the seals 43a, 43b from the sliding surfaces. |
