Retractable bollard comprises cylinder with slides on its inner wall which move between it and concentric guide tube to raise and lower bollard.

摘要

The retractable bollard comprises a cylinder (6) with slides (10, 11) on its inner wall which move between it and a concentric guide tube (12) to raise and lower the bollard. Electromagnetic position detectors (15, 16) cooperate with a lug (17) on the outside of the bollard to detect whether it is raised or lowered.