Granted Patent
Utility
US 4,248,302 · App. 06/033,514
Method and apparatus for recovering viscous petroleum from tar sand
Inventor:
Ronald K. Churchman
Patented Case
View Patent ↗
Granted: Feb 3, 1981
Filed: Apr 26, 1979
Inventor
Ronald K. Churchman
Assignee (at issue)
Otis Engineering 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.