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Priority claimed from PL118299Aexternal-prioritypatent/PL56867B1/pl
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Publication of BE708882ApublicationCriticalpatent/BE708882A/xx
E21C27/00—Machines which completely free the mineral from the seam
E21C27/01—Machines which completely free the mineral from the seam specially adapted for removing overhanging coal
E—FIXED CONSTRUCTIONS
E21—EARTH OR ROCK DRILLING; MINING
E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
E21D23/00—Mine roof supports for step- by- step movement, e.g. in combination with provisions for shifting of conveyors, mining machines, or guides therefor
E21D23/04—Structural features of the supporting construction, e.g. linking members between adjacent frames or sets of props; Means for counteracting lateral sliding on inclined floor
E21D23/06—Special mine caps or special tops of pit-props for permitting step-by-step movement
