Granted Patent
Utility
US 4,196,588 · App. 05/901,409
Margin valve
Inventor:
Howard L. Johnson
Patented Case
View Patent ↗
Granted: Apr 8, 1980
Filed: May 1, 1978
Inventor
Howard L. Johnson
Assignee (at issue)
Caterpillar Tractor Co.
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.