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公开(公告)号：US2565730A
公开(公告)日：1951-08-28
申请号：US8932449
申请日：1949-04-23
Applicant: M O JOHNSTON
Inventor： BLAINE JOHNSTON , LUIRETTE ROBERT B , SINCLAIR GEORGE W
IPC: E21B19/00
CPC classification number: E21B19/00
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