Patent classifications
E
FIXED CONSTRUCTIONS
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E21
EARTH OR ROCK DRILLING; MINING
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E21C
MINING OR QUARRYING
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27/00
Machines which completely free the mineral from the seam
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E21C27/20
Mineral freed by means not involving slitting
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E21C27/28
by percussive drills with breaking-down means, e.g. wedge-shaped tools
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