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公开(公告)号：US2274698A
公开(公告)日：1942-03-03
申请号：US39417241
申请日：1941-05-19
Applicant: CLEVELAND ROCK DRILL CO
Inventor： ALBERT FEUCHT , SCHMIDT THEODORE A
IPC: E21B19/24
CPC classification number: E21B19/24
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