Granted Patent
Utility
US 6,218,002 · App. 08/991,297
Concrete mix containing polystyrene beads
Inventor:
Erik W. Wehtje
Patented Case
View Patent ↗
Granted: Apr 17, 2001
Filed: Dec 16, 1997
Inventor
Erik W. Wehtje
Assignee (at issue)
PolySource LLC
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.