| 摘要 |
A mine roof support has a base and a roof shield pivoted to the base and carrying at its upper end a pivoted cap which is urged upwardly against the mine roof by a hydraulic pit prop reacting between the cap and the base. The lower end of the roof shield is connected to the base by two links each having a pivot cooperating with a pivot on the roof shield, and a pivot cooperating with a pivot on the base. In addition, the base and/or the lower end of the roof shield has an auxiliary for each link and each link has an auxiliary pivot which can be connected with one of the auxiliary pivots of the base or lower end.
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