| 摘要 |
A blade mechanism pivots on an anchoring device, and has an outer face which travels over the entire path of the outer part of the guide face. The outer face can be concave, and the blade mechanism can have the shape of a quadrant of a cylinder parallel to the pivot axis. It can be actuated by a hydraulic ram, with an outer casing incorporating the pivot pin. The anchoring device can be a pit prop. The material for use in backfilling does not spill behind on the forward stroke and cause obstruction on the backward stroke. |
