Granted Patent
Utility
US 4,712,992 · App. 06/873,646
Extruder with screw having core portion of polygonal cross-section
Inventor:
Heung T. Kim
Patented Case
View Patent ↗
Granted: Dec 15, 1987
Filed: Jun 12, 1986
Inventor
Heung T. Kim
Assignee (at issue)
B. F. Goodrich Company
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.