| 摘要 |
The automatic locking in top and bottom positions of bollards, retractable in the ground, for preventing access to vehicles, is composed of a vertical non-machined cylindrical shaft (1). There are two folded sheet metal cams (2,8), fixed on a spindle (4) and held by springs (3) made from round curved and folded metal wires. The upper cam retains the bollard in its top position and the lower cam holds it in its bottom position. The cams by their U-shape are only able to hold parts falling by gravity such as sand, leaves, gravel or dust by gravity. The springs which are fixed to the cams allow the cams to operate in extreme corrosive conditions such as sand and water.
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