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Mine-roof support control means
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Patent number 4,476,898
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Issue date Oct 16, 1984
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Hermann Hemscheidt Maschinenfabrik GmbH & Co.
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Karl Krieger
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E21 - EARTH DRILLING MINING
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Hydraulically-operated devices
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Patent number 4,422,808
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Issue date Dec 27, 1983
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Dowty Mining Equipment Limited
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Stephen P. Cook
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E21 - EARTH DRILLING MINING
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Longwall mining apparatus
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Patent number 4,109,472
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Issue date Aug 29, 1978
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Dowty Mining Equipment Limited
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Robert G. Harris
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E21 - EARTH DRILLING MINING
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3541926
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Patent number 3,541,926
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Issue date Nov 24, 1970
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E21 - EARTH DRILLING MINING
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3514961
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Patent number 3,514,961
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Issue date Jun 2, 1970
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E21 - EARTH DRILLING MINING
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3246576
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Patent number 3,246,576
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Issue date Apr 19, 1966
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E21 - EARTH DRILLING MINING