Patent classifications
E
FIXED CONSTRUCTIONS
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E21
EARTH OR ROCK DRILLING; MINING
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E21D
SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
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15/00
Props; Chocks; , e.g. made of flexible containers filled with backfilling material
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E21D15/16
with parts held together by positive means, with or without relative sliding movement when the prop is subject to excessive pressure
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E21D15/18
with one part resting on a supporting medium, e.g. rubber, sand, bitumen, lead, located in the other part, with or without expulsion or displacement of the medium upon excessive pressure
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