Granted Patent
Utility
US 4,470,938 · App. 06/412,438
Method and apparatus for extrusion of thermoplastic foam
Inventor:
D. Emil Johnson
Patented Case
View Patent ↗
Granted: Sep 11, 1984
Filed: Aug 27, 1982
Inventor
D. Emil Johnson
Assignee (at issue)
Mobil Oil 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.