Granted Patent
Utility
US 5,288,219 · App. 07/674,589
Air ring for controlling blown film thickness
Inventor:
David J. Smith
Patented Case
View Patent ↗
Granted: Feb 22, 1994
Filed: Mar 25, 1991
Inventor
David J. Smith
Assignee (at issue)
Battenfeld Gloucester Engineering 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.