| 摘要 |
A mine roof support comprising a floor-engageable member, a roof-engageable member such as a canopy extending forwardly of the floor-engaging member, a first extensible leg secured between the floor-engaging member and the canopy, a linkage, which may include a shield, mounted on the floor-engaging member and pivotally connected to the roof-engageable member at its rear end and a second extensible leg secured between the floor-engaging member and the linkage. The linkage is preferably operative to constrain its pivotal connection to the canopy to move upward and downward in a fixed path relative to the floor-engaging member. |
