| 摘要 |
The invention refers to a movable trestle of approximately rectangular horizontal projection and serving the purpose of supporting the roof in underground cavities in particular serving the purpose of securing the excavation edge when recovering pillars in coal mining, comprising a cap (2) supported against a base frame (1) by hydraulically extensible props extending approximately in vertical direction to stratification. The lower portion of the trestle is, preferably at all sides, covered by a stationary shielding means against the ingress of rubble into its interior and horizontal protective plates (3) overlapping one another in a scale-like manner and being guided on sliding plates (8) for relative shifting movement in height direction are provided within the area of the expandable portion of the trestle. The protective plates (3) are arranged on the rear side (12) of the trestle and on the both sides (10, 11) adjoining the rear side of the trestle. The protective plates (3) extend over the whole width of the trestle and are guided and held at their ends by means of sliding plates. The respective upper protective plate overlaps the respective associated lower protective plate at its outer side. In this manner, it is possible to support in coal mining, in particular when recovering pillars, the excavated material of the mine face and the excavated material of the recovered pillars and to move the trestle in forward direction by means of the caterpillars (18) when having finished the work.
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