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Patent Searching and Data


Document Type and Number:
Japanese Patent JPH044988
Kind Code:
U
Application Number:
JP4384890U
Publication Date:
January 17, 1992
Filing Date:
April 24, 1990
Export Citation:
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International Classes:
E21B6/02; E21B3/00; E21C37/02; (IPC1-7): E21C37/02; E21C1/12
Domestic Patent References:
JPS61233197A1986-10-17
JPS57174570U1982-11-04



 
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