Granted Patent
Utility
US 4,237,769 · App. 05/892,914
Relief valves and mine props incorporating the same
Inventor:
Arthur J. Williams
Patented Case
View Patent ↗
Granted: Dec 9, 1980
Filed: Apr 3, 1978
Inventor
Arthur J. Williams
Assignee (at issue)
Commercial Shearing, Inc.
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.