| 摘要 |
A mine roof support has a roof engaging structure 13 and a floor engaging base 14, spaced apart by extensible hydraulic jack means 15 and 16. The roof engaging structure and the base are interconnected by a pivotal linkage device 23, 24 arranged so that, throughout its range of working movement, a pivot point of the linkage performs substantially greater movement in the vertical direction than in the horizontal direction. This reduces the effect of problems arising from the linkage device projecting substantially into the goaf area of a mine working or into the walkway area of the support. In a preferred embodiment the linkage device comprises a parallelogram type linkage. |
