Granted Patent
Utility
US 4,170,448 · App. 05/826,586
Assembly for forming the bell of a bell spigot joint
Inventor:
David W. French
Patented Case
View Patent ↗
Granted: Oct 9, 1979
Filed: Aug 22, 1977
Inventor
David W. French
Assignee (at issue)
Johns Manville
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.