Granted Patent
Utility
US 6,499,239 · App. 09/554,551
Method for extracting and grading sand
Inventors:
Hendrikus Van Berk, Sjerp Zeldenrust
Patented Case
View Patent ↗
Granted: Dec 31, 2002
Filed: Jan 26, 2001
Inventors
Hendrikus Van Berk
Sjerp Zeldenrust
Assignee (at issue)
De Groot Nijkerk Machinefabriek B.V.
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.