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公开(公告)号：US2155744A
公开(公告)日：1939-04-25
申请号：US8671736
申请日：1936-06-23
Applicant: LESLIE A LAYNE
Inventor： WESTRUM COLBY VAN
IPC: E21B43/08
CPC classification number: E21B43/088 , Y10T29/49602
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