Granted Patent
Utility
US 5,031,696 · App. 07/556,891
Casing hanger and seal
Inventor:
John M. Zwiegel
Patented Case
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Granted: Jul 16, 1991
Filed: Jul 23, 1990
Inventor
John M. Zwiegel
Assignee (at issue)
Cooper Industries Holdings
This patent predates the USPTO's electronic file wrapper — prosecution documents from this era exist only in the Patent Office's paper records. A certified copy of the file history can be ordered from the USPTO's paper archives.