Granted Patent
Utility
US 4,628,721 · App. 06/753,327
Method of roll forming cylindrical pipe
Inventor:
Calvin C. Williamson
Patented Case
View Patent ↗
Granted: Dec 16, 1986
Filed: Jul 9, 1985
Inventor
Calvin C. Williamson
Assignee (at issue)
Kaiser Steel Corporation
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.