Granted Patent
Utility
US 4,291,889 · App. 06/179,021
Seal for wellheads
Inventor:
Phillip Hardcastle
Patented Case
View Patent ↗
Granted: Sep 29, 1981
Filed: Aug 18, 1980
Inventor
Phillip Hardcastle
Assignee (at issue)
Cactus Pipe & Supply Co., Inc.
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.