Granted Patent
Utility
US 6,161,422 · App. 09/071,445
Sand testing method and apparatus
Inventors:
Perry L. Thomas, Ronald W. Roethlisberger
Patented Case
View Patent ↗
Granted: Dec 19, 2000
Filed: May 1, 1998
Inventors
Perry L. Thomas
Ronald W. Roethlisberger
Assignee (at issue)
Hartley Controls 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.