-
公开(公告)号：US2263639A
公开(公告)日：1941-11-25
申请号：US28635639
申请日：1939-07-25
Applicant: ROLAND R CRUM
Inventor： ALFRED MUHLBACH
IPC: E21B25/04
CPC classification number: E21B25/04
Search Results
1
records
(took 0.019 seconds)
筛选
AND
AND
过滤
NOT
NOT
Scan to Join
