| 摘要 |
The device has a pair of anchoring cams (11, 12) mounted in rotation and in opposition on a common support axis. The cams (11, 12) have support surfaces (11a, 12a), respectively. The surface (11a) presents a convex face and the surface (12a) presents a concave face so as to obtain three support zones or points (A, B, C) when the cams are in blocking position.
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